diff --git a/js/src/asmjs/AsmJS.cpp b/js/src/asmjs/AsmJS.cpp
index 085790f91ba3..ab274bfc76c2 100644
--- a/js/src/asmjs/AsmJS.cpp
+++ b/js/src/asmjs/AsmJS.cpp
@@ -2084,10 +2084,7 @@ class MOZ_STACK_CLASS ModuleValidator
         uint32_t sigIndex;
         if (!declareSig(Move(sig), &sigIndex))
             return false;
-        uint32_t globalDataOffset;
-        if (!mg_.allocateGlobalBytes(Module::SizeOfImportExit, sizeof(void*), &globalDataOffset))
-            return false;
-        if (!mg_.initImport(*importIndex, sigIndex, globalDataOffset))
+        if (!mg_.initImport(*importIndex, sigIndex))
             return false;
         return importMap_.add(p, NamedSig(name, mg_.sig(sigIndex)), *importIndex);
     }
@@ -7148,7 +7145,7 @@ ValidateFFI(JSContext* cx, const AsmJSGlobal& global, HandleValue importVal,
     if (!GetDataProperty(cx, importVal, field, &v))
         return false;
 
-    if (!v.isObject() || !v.toObject().is<JSFunction>())
+    if (!IsFunctionObject(v))
         return LinkFail(cx, "FFI imports must be functions");
 
     ffis[global.ffiIndex()].set(&v.toObject().as<JSFunction>());
diff --git a/js/src/asmjs/Wasm.cpp b/js/src/asmjs/Wasm.cpp
index c7c9eb6cb2f2..5dbef88f7c27 100644
--- a/js/src/asmjs/Wasm.cpp
+++ b/js/src/asmjs/Wasm.cpp
@@ -314,6 +314,21 @@ DecodeSignatureSection(JSContext* cx, Decoder& d, ModuleGeneratorData* init)
     return true;
 }
 
+static bool
+DecodeSignatureIndex(JSContext* cx, Decoder& d, const ModuleGeneratorData& init,
+                     const DeclaredSig** sig)
+{
+    uint32_t sigIndex;
+    if (!d.readVarU32(&sigIndex))
+        return Fail(cx, d, "expected signature index");
+
+    if (sigIndex >= init.sigs.length())
+        return Fail(cx, d, "signature index out of range");
+
+    *sig = &init.sigs[sigIndex];
+    return true;
+}
+
 static bool
 DecodeDeclarationSection(JSContext* cx, Decoder& d, ModuleGeneratorData* init)
 {
@@ -332,14 +347,8 @@ DecodeDeclarationSection(JSContext* cx, Decoder& d, ModuleGeneratorData* init)
         return false;
 
     for (uint32_t i = 0; i < numDecls; i++) {
-        uint32_t sigIndex;
-        if (!d.readVarU32(&sigIndex))
-            return Fail(cx, d, "expected declaration signature index");
-
-        if (sigIndex >= init->sigs.length())
-            return Fail(cx, d, "declaration signature index out of range");
-
-        init->funcSigs[i] = &init->sigs[sigIndex];
+        if (!DecodeSignatureIndex(cx, d, *init, &init->funcSigs[i]))
+            return false;
     }
 
     if (!d.finishSection(sectionStart))
@@ -348,6 +357,81 @@ DecodeDeclarationSection(JSContext* cx, Decoder& d, ModuleGeneratorData* init)
     return true;
 }
 
+struct ImportName
+{
+    UniqueChars module;
+    UniqueChars func;
+
+    ImportName(UniqueChars module, UniqueChars func)
+      : module(Move(module)), func(Move(func))
+    {}
+    ImportName(ImportName&& rhs)
+      : module(Move(rhs.module)), func(Move(rhs.func))
+    {}
+};
+
+typedef Vector<ImportName, 0, SystemAllocPolicy> ImportNameVector;
+
+static bool
+DecodeImport(JSContext* cx, Decoder& d, ModuleGeneratorData* init, ImportNameVector* importNames)
+{
+    if (!d.readCStringIf(FuncSubsection))
+        return Fail(cx, d, "expected 'func' tag");
+
+    const DeclaredSig* sig;
+    if (!DecodeSignatureIndex(cx, d, *init, &sig))
+        return false;
+
+    if (!init->imports.emplaceBack(sig))
+        return false;
+
+    const char* moduleStr;
+    if (!d.readCString(&moduleStr))
+        return Fail(cx, d, "expected import module name");
+
+    if (!*moduleStr)
+        return Fail(cx, d, "module name cannot be empty");
+
+    UniqueChars moduleName = DuplicateString(moduleStr);
+    if (!moduleName)
+        return false;
+
+    const char* funcStr;
+    if (!d.readCString(&funcStr))
+        return Fail(cx, d, "expected import func name");
+
+    UniqueChars funcName = DuplicateString(funcStr);
+    if (!funcName)
+        return false;
+
+    return importNames->emplaceBack(Move(moduleName), Move(funcName));
+}
+
+static bool
+DecodeImportSection(JSContext* cx, Decoder& d, ModuleGeneratorData* init, ImportNameVector* imports)
+{
+    if (!d.readCStringIf(ImportSection))
+        return true;
+
+    uint32_t sectionStart;
+    if (!d.startSection(&sectionStart))
+        return Fail(cx, d, "expected import section byte size");
+
+    uint32_t numImports;
+    if (!d.readVarU32(&numImports))
+        return Fail(cx, d, "expected number of imports");
+
+    for (uint32_t i = 0; i < numImports; i++) {
+        if (!DecodeImport(cx, d, init, imports))
+            return false;
+    }
+
+    if (!d.finishSection(sectionStart))
+        return Fail(cx, d, "import section byte size mismatch");
+
+    return true;
+}
+
 static bool
 DecodeExport(JSContext* cx, Decoder& d, ModuleGenerator& mg, ExportMap* exportMap)
 {
@@ -518,7 +602,8 @@ DecodeUnknownSection(JSContext* cx, Decoder& d)
 
 static bool
 DecodeModule(JSContext* cx, UniqueChars filename, const uint8_t* bytes, uint32_t length,
-             MutableHandle<WasmModuleObject*> moduleObj, ExportMap* exportMap)
+             ImportNameVector* importNames, ExportMap* exportMap,
+             MutableHandle<WasmModuleObject*> moduleObj)
 {
     Decoder d(bytes, bytes + length);
 
@@ -539,6 +624,9 @@ DecodeModule(JSContext* cx, UniqueChars filename, const uint8_t* bytes, uint32_t
     if (!DecodeDeclarationSection(cx, d, init.get()))
         return false;
 
+    if (!DecodeImportSection(cx, d, init.get(), importNames))
+        return false;
+
     ModuleGenerator mg(cx);
     if (!mg.init(Move(init)))
         return false;
@@ -578,7 +666,49 @@ DecodeModule(JSContext* cx, UniqueChars filename, const uint8_t* bytes, uint32_t
 }
 
 /*****************************************************************************/
-// JS entry poitns
+// JS entry points
+
+static bool
+GetProperty(JSContext* cx, HandleObject obj, const char* utf8Chars, MutableHandleValue v)
+{
+    JSAtom* atom = AtomizeUTF8Chars(cx, utf8Chars, strlen(utf8Chars));
+    if (!atom)
+        return false;
+
+    RootedId id(cx, AtomToId(atom));
+    return GetProperty(cx, obj, obj, id, v);
+}
+
+static bool
+ImportFunctions(JSContext* cx, HandleObject importObj, const ImportNameVector& importNames,
+                MutableHandle<FunctionVector> imports)
+{
+    if (!importNames.empty() && !importObj)
+        return Fail(cx, "no import object given");
+
+    for (const ImportName& name : importNames) {
+        RootedValue v(cx);
+        if (!GetProperty(cx, importObj, name.module.get(), &v))
+            return false;
+
+        if (*name.func.get()) {
+            if (!v.isObject())
+                return Fail(cx, "import object field is not an Object");
+
+            RootedObject obj(cx, &v.toObject());
+            if (!GetProperty(cx, obj, name.func.get(), &v))
+                return false;
+        }
+
+        if (!IsFunctionObject(v))
+            return Fail(cx, "import object field is not a Function");
+
+        if (!imports.append(&v.toObject().as<JSFunction>()))
+            return false;
+    }
+
+    return true;
+}
 
 static bool
 SupportsWasm(JSContext* cx)
@@ -636,15 +766,6 @@ WasmEval(JSContext* cx, unsigned argc, Value* vp)
         return false;
     }
 
-    if (!args.get(1).isUndefined() && !args.get(1).isObject()) {
-        ReportUsageError(cx, callee, "Second argument, if present, must be an Object");
-        return false;
-    }
-
-    UniqueChars filename;
-    if (!DescribeScriptedCaller(cx, &filename))
-        return false;
-
     Rooted<ArrayBufferObject*> code(cx, &args[0].toObject().as<ArrayBufferObject>());
     const uint8_t* bytes = code->dataPointer();
     uint32_t length = code->byteLength();
@@ -656,9 +777,23 @@ WasmEval(JSContext* cx, unsigned argc, Value* vp)
         bytes = copy.begin();
     }
 
-    Rooted<WasmModuleObject*> moduleObj(cx);
+    RootedObject importObj(cx);
+    if (!args.get(1).isUndefined()) {
+        if (!args.get(1).isObject()) {
+            ReportUsageError(cx, callee, "Second argument, if present, must be an Object");
+            return false;
+        }
+        importObj = &args[1].toObject();
+    }
+
+    UniqueChars filename;
+    if (!DescribeScriptedCaller(cx, &filename))
+        return false;
+
+    ImportNameVector importNames;
     ExportMap exportMap;
-    if (!DecodeModule(cx, Move(filename), bytes, length, &moduleObj, &exportMap)) {
+    Rooted<WasmModuleObject*> moduleObj(cx);
+    if (!DecodeModule(cx, Move(filename), bytes, length, &importNames, &exportMap, &moduleObj)) {
         if (!cx->isExceptionPending())
             ReportOutOfMemory(cx);
         return false;
@@ -671,8 +806,8 @@ WasmEval(JSContext* cx, unsigned argc, Value* vp)
         return Fail(cx, "Heap not implemented yet");
 
     Rooted<FunctionVector> imports(cx, FunctionVector(cx));
-    if (module.imports().length() > 0)
-        return Fail(cx, "Imports not implemented yet");
+    if (!ImportFunctions(cx, importObj, importNames, &imports))
+        return false;
 
     RootedObject exportObj(cx);
     if (!module.dynamicallyLink(cx, moduleObj, heap, imports, exportMap, &exportObj))
diff --git a/js/src/asmjs/WasmBinary.h b/js/src/asmjs/WasmBinary.h
index 4c9a5fd94750..4a8e85ffd00e 100644
--- a/js/src/asmjs/WasmBinary.h
+++ b/js/src/asmjs/WasmBinary.h
@@ -35,6 +35,7 @@ static const uint32_t EncodingVersion = -1;     // experimental
 // Module section names:
 static const char SigSection[] =     "sig";
 static const char DeclSection[] =    "decl";
+static const char ImportSection[] =  "import";
 static const char ExportSection[] =  "export";
 static const char CodeSection[] =    "code";
 static const char EndSection[] =     "";
diff --git a/js/src/asmjs/WasmGenerator.cpp b/js/src/asmjs/WasmGenerator.cpp
index 505a9899bb08..39fd1817dded 100644
--- a/js/src/asmjs/WasmGenerator.cpp
+++ b/js/src/asmjs/WasmGenerator.cpp
@@ -128,8 +128,12 @@ ModuleGenerator::init(UniqueModuleGeneratorData shared, ModuleKind kind)
     if (kind == ModuleKind::Wasm) {
         numSigs_ = shared_->sigs.length();
         module_->numFuncs = shared_->funcSigs.length();
-        for (uint32_t i = 0; i < shared_->imports.length(); i++) {
-            if (!addImport(*shared_->imports[i].sig, shared_->imports[i].globalDataOffset))
+        module_->globalBytes = AlignBytes(module_->globalBytes, sizeof(void*));
+        for (ModuleImportGeneratorData& import : shared_->imports) {
+            MOZ_ASSERT(!import.globalDataOffset);
+            import.globalDataOffset = module_->globalBytes;
+            module_->globalBytes += Module::SizeOfImportExit;
+            if (!addImport(*import.sig, import.globalDataOffset))
                 return false;
         }
     }
@@ -302,8 +306,12 @@ ModuleGenerator::funcSig(uint32_t funcIndex) const
 }
 
 bool
-ModuleGenerator::initImport(uint32_t importIndex, uint32_t sigIndex, uint32_t globalDataOffset)
+ModuleGenerator::initImport(uint32_t importIndex, uint32_t sigIndex)
 {
+    uint32_t globalDataOffset;
+    if (!allocateGlobalBytes(Module::SizeOfImportExit, sizeof(void*), &globalDataOffset))
+        return false;
+
     MOZ_ASSERT(isAsmJS());
     MOZ_ASSERT(importIndex == module_->imports.length());
     if (!addImport(sig(sigIndex), globalDataOffset))
diff --git a/js/src/asmjs/WasmGenerator.h b/js/src/asmjs/WasmGenerator.h
index 508982ccf4b2..cc1be7e8d358 100644
--- a/js/src/asmjs/WasmGenerator.h
+++ b/js/src/asmjs/WasmGenerator.h
@@ -48,8 +48,8 @@ struct SlowFunction
 typedef Vector<SlowFunction> SlowFunctionVector;
 
 // The ModuleGeneratorData holds all the state shared between the
-// ModuleGenerator and ModuleGeneratorThreadView. The ModuleGeneratorData is
-// encapsulated by ModuleGenerator/ModuleGeneratorThreadView classes which
+// ModuleGenerator and ModuleGeneratorThreadView. The ModuleGeneratorData
+// is encapsulated by ModuleGenerator/ModuleGeneratorThreadView classes which
 // present a race-free interface to the code in each thread assuming any given
 // element is initialized by the ModuleGenerator thread before an index to that
 // element is written to Bytecode sent to a ModuleGeneratorThreadView thread.
@@ -57,15 +57,17 @@ typedef Vector<SlowFunction> SlowFunctionVector;
 
 struct ModuleImportGeneratorData
 {
-    DeclaredSig* sig;
+    const DeclaredSig* sig;
     uint32_t globalDataOffset;
+
+    ModuleImportGeneratorData() : sig(nullptr), globalDataOffset(0) {}
+    explicit ModuleImportGeneratorData(const DeclaredSig* sig) : sig(sig), globalDataOffset(0) {}
 };
 
 typedef Vector<ModuleImportGeneratorData, 0, SystemAllocPolicy> ModuleImportGeneratorDataVector;
 
-// Global variable descriptor, in asm.js only.
-
-struct AsmJSGlobalVariable {
+struct AsmJSGlobalVariable
+{
     ExprType type;
     unsigned globalDataOffset;
     bool isConst;
@@ -159,6 +161,7 @@ class MOZ_STACK_CLASS ModuleGenerator
     bool finishTask(IonCompileTask* task);
     bool addImport(const Sig& sig, uint32_t globalDataOffset);
     bool startedFuncDefs() const { return !!threadView_; }
+    bool allocateGlobalBytes(uint32_t bytes, uint32_t align, uint32_t* globalDataOffset);
 
   public:
     explicit ModuleGenerator(ExclusiveContext* cx);
@@ -171,8 +174,7 @@ class MOZ_STACK_CLASS ModuleGenerator
     jit::MacroAssembler& masm() { return masm_; }
     const Uint32Vector& funcEntryOffsets() const { return funcEntryOffsets_; }
 
-    // Global data:
-    bool allocateGlobalBytes(uint32_t bytes, uint32_t align, uint32_t* globalDataOffset);
+    // asm.js global variables:
     bool allocateGlobalVar(ValType type, bool isConst, uint32_t* index);
     const AsmJSGlobalVariable& globalVar(unsigned index) const { return shared_->globals[index]; }
 
@@ -187,7 +189,7 @@ class MOZ_STACK_CLASS ModuleGenerator
     const DeclaredSig& funcSig(uint32_t funcIndex) const;
 
     // Imports:
-    bool initImport(uint32_t importIndex, uint32_t sigIndex, uint32_t globalDataOffset);
+    bool initImport(uint32_t importIndex, uint32_t sigIndex);
     uint32_t numImports() const;
     const ModuleImportGeneratorData& import(uint32_t index) const;
     bool defineImport(uint32_t index, ProfilingOffsets interpExit, ProfilingOffsets jitExit);
diff --git a/js/src/asmjs/WasmModule.h b/js/src/asmjs/WasmModule.h
index 4f19ae13e8be..9352ab66f8fe 100644
--- a/js/src/asmjs/WasmModule.h
+++ b/js/src/asmjs/WasmModule.h
@@ -177,11 +177,9 @@ class Import
         return pod.exitGlobalDataOffset_;
     }
     uint32_t interpExitCodeOffset() const {
-        MOZ_ASSERT(pod.interpExitCodeOffset_);
         return pod.interpExitCodeOffset_;
     }
     uint32_t jitExitCodeOffset() const {
-        MOZ_ASSERT(pod.jitExitCodeOffset_);
         return pod.jitExitCodeOffset_;
     }
 
diff --git a/js/src/asmjs/WasmText.cpp b/js/src/asmjs/WasmText.cpp
index df2a3e7ba4c6..ddc8e2a708f3 100644
--- a/js/src/asmjs/WasmText.cpp
+++ b/js/src/asmjs/WasmText.cpp
@@ -95,6 +95,7 @@ enum class WasmAstKind
     Export,
     Func,
     GetLocal,
+    Import,
     Module,
     Nop,
     SetLocal
@@ -213,6 +214,21 @@ class WasmAstFunc : public WasmAstNode
     WasmAstExpr* maybeBody() const { return maybeBody_; }
 };
 
+class WasmAstImport : public WasmAstNode
+{
+    TwoByteChars module_;
+    TwoByteChars func_;
+    uint32_t sigIndex_;
+
+  public:
+    WasmAstImport(TwoByteChars module, TwoByteChars func, uint32_t sigIndex)
+      : WasmAstNode(WasmAstKind::Import), module_(module), func_(func), sigIndex_(sigIndex)
+    {}
+    TwoByteChars module() const { return module_; }
+    TwoByteChars func() const { return func_; }
+    uint32_t sigIndex() const { return sigIndex_; }
+};
+
 class WasmAstExport : public WasmAstNode
 {
     TwoByteChars name_;
@@ -229,12 +245,14 @@ class WasmAstExport : public WasmAstNode
 class WasmAstModule : public WasmAstNode
 {
     typedef WasmAstVector<WasmAstFunc*> FuncVector;
+    typedef WasmAstVector<WasmAstImport*> ImportVector;
     typedef WasmAstVector<WasmAstExport*> ExportVector;
     typedef WasmAstVector<WasmAstSig*> SigVector;
     typedef WasmAstHashMap<WasmAstSig*, uint32_t, WasmAstSig> SigMap;
 
     LifoAlloc& lifo_;
     FuncVector funcs_;
+    ImportVector imports_;
     ExportVector exports_;
     SigVector sigs_;
     SigMap sigMap_;
@@ -244,6 +262,7 @@ class WasmAstModule : public WasmAstNode
       : WasmAstNode(WasmAstKind::Module),
         lifo_(lifo),
         funcs_(lifo),
+        imports_(lifo),
         exports_(lifo),
         sigs_(lifo),
         sigMap_(lifo)
@@ -270,6 +289,12 @@ class WasmAstModule : public WasmAstNode
     const FuncVector& funcs() const {
         return funcs_;
     }
+    const ImportVector& imports() const {
+        return imports_;
+    }
+    bool append(WasmAstImport* imp) {
+        return imports_.append(imp);
+    }
     bool append(WasmAstExport* exp) {
         return exports_.append(exp);
     }
@@ -294,6 +319,7 @@ class WasmToken
         Export,
         Func,
         GetLocal,
+        Import,
         Integer,
         Local,
         Module,
@@ -496,14 +522,12 @@ class WasmTokenStream
             if (consume(end_, MOZ_UTF16("32"))) {
                 if (consume(end_, MOZ_UTF16(".const")))
                     return WasmToken(WasmToken::Const, ValType::F32, begin, cur_);
-                else
-                    return WasmToken(WasmToken::ValueType, ValType::F32, begin, cur_);
+                return WasmToken(WasmToken::ValueType, ValType::F32, begin, cur_);
             }
             if (consume(end_, MOZ_UTF16("64"))) {
                 if (consume(end_, MOZ_UTF16(".const")))
                     return WasmToken(WasmToken::Const, ValType::F64, begin, cur_);
-                else
-                    return WasmToken(WasmToken::ValueType, ValType::F64, begin, cur_);
+                return WasmToken(WasmToken::ValueType, ValType::F64, begin, cur_);
             }
             break;
 
@@ -516,15 +540,15 @@ class WasmTokenStream
             if (consume(end_, MOZ_UTF16("32"))) {
                 if (consume(end_, MOZ_UTF16(".const")))
                     return WasmToken(WasmToken::Const, ValType::I32, begin, cur_);
-                else
-                    return WasmToken(WasmToken::ValueType, ValType::I32, begin, cur_);
+                return WasmToken(WasmToken::ValueType, ValType::I32, begin, cur_);
             }
             if (consume(end_, MOZ_UTF16("64"))) {
                 if (consume(end_, MOZ_UTF16(".const")))
                     return WasmToken(WasmToken::Const, ValType::I64, begin, cur_);
-                else
-                    return WasmToken(WasmToken::ValueType, ValType::I64, begin, cur_);
+                return WasmToken(WasmToken::ValueType, ValType::I64, begin, cur_);
             }
+            if (consume(end_, MOZ_UTF16("mport")))
+                return WasmToken(WasmToken::Import, begin, cur_);
             break;
 
           case 'l':
@@ -737,6 +761,30 @@ ParseExprInsideParens(WasmParseContext& c)
     }
 }
 
+static bool
+ParseValueType(WasmParseContext& c, WasmAstValTypeVector* vec)
+{
+    WasmToken valueType;
+    return c.ts.match(WasmToken::ValueType, &valueType, c.error) &&
+           vec->append(valueType.valueType());
+}
+
+static bool
+ParseResult(WasmParseContext& c, ExprType* result)
+{
+    if (*result != ExprType::Void) {
+        c.ts.generateError(c.ts.peek(), c.error);
+        return false;
+    }
+
+    WasmToken valueType;
+    if (!c.ts.match(WasmToken::ValueType, &valueType, c.error))
+        return false;
+
+    *result = ToExprType(valueType.valueType());
+    return true;
+}
+
 static WasmAstFunc*
 ParseFunc(WasmParseContext& c, WasmAstModule* module)
 {
@@ -746,44 +794,27 @@ ParseFunc(WasmParseContext& c, WasmAstModule* module)
 
     WasmAstExpr* maybeBody = nullptr;
     while (c.ts.getIf(WasmToken::OpenParen) && !maybeBody) {
-        WasmToken field = c.ts.get();
-
-        switch (field.kind()) {
-          case WasmToken::Local: {
-            WasmToken valueType;
-            if (!c.ts.match(WasmToken::ValueType, &valueType, c.error))
-                return nullptr;
-            if (!vars.append(valueType.valueType()))
+        WasmToken token = c.ts.get();
+        switch (token.kind()) {
+          case WasmToken::Local:
+            if (!ParseValueType(c, &vars))
                 return nullptr;
             break;
-          }
-          case WasmToken::Param: {
-            WasmToken valueType;
-            if (!c.ts.match(WasmToken::ValueType, &valueType, c.error))
-                return nullptr;
-            if (!args.append(valueType.valueType()))
+          case WasmToken::Param:
+            if (!ParseValueType(c, &args))
                 return nullptr;
             break;
-          }
-          case WasmToken::Result: {
-            if (result != ExprType::Void) {
-                c.ts.generateError(field, c.error);
+          case WasmToken::Result:
+            if (!ParseResult(c, &result))
                 return nullptr;
-            }
-            WasmToken valueType;
-            if (!c.ts.match(WasmToken::ValueType, &valueType, c.error))
-                return nullptr;
-            result = ToExprType(valueType.valueType());
             break;
-          }
           default:
-            c.ts.unget(field);
+            c.ts.unget(token);
             maybeBody = ParseExprInsideParens(c);
             if (!maybeBody)
                 return nullptr;
             break;
         }
-
         if (!c.ts.match(WasmToken::CloseParen, c.error))
             return nullptr;
     }
@@ -795,6 +826,46 @@ ParseFunc(WasmParseContext& c, WasmAstModule* module)
     return new(c.lifo) WasmAstFunc(sigIndex, Move(vars), maybeBody);
 }
 
+static WasmAstImport*
+ParseImport(WasmParseContext& c, WasmAstModule* module)
+{
+    WasmToken moduleName;
+    if (!c.ts.match(WasmToken::Text, &moduleName, c.error))
+        return nullptr;
+
+    WasmToken funcName;
+    if (!c.ts.match(WasmToken::Text, &funcName, c.error))
+        return nullptr;
+
+    WasmAstValTypeVector args(c.lifo);
+    ExprType result = ExprType::Void;
+
+    while (c.ts.getIf(WasmToken::OpenParen)) {
+        WasmToken token = c.ts.get();
+        switch (token.kind()) {
+          case WasmToken::Param:
+            if (!ParseValueType(c, &args))
+                return nullptr;
+            break;
+          case WasmToken::Result:
+            if (!ParseResult(c, &result))
+                return nullptr;
+            break;
+          default:
+            c.ts.generateError(token, c.error);
+            return nullptr;
+        }
+        if (!c.ts.match(WasmToken::CloseParen, c.error))
+            return nullptr;
+    }
+
+    uint32_t sigIndex;
+    if (!module->declare(WasmAstSig(Move(args), result), &sigIndex))
+        return nullptr;
+
+    return new(c.lifo) WasmAstImport(moduleName.text(), funcName.text(), sigIndex);
+}
+
 static WasmAstExport*
 ParseExport(WasmParseContext& c)
 {
@@ -827,6 +898,12 @@ TextToAst(const char16_t* text, LifoAlloc& lifo, UniqueChars* error)
         WasmToken section = c.ts.get();
 
         switch (section.kind()) {
+          case WasmToken::Import: {
+            WasmAstImport* imp = ParseImport(c, module);
+            if (!imp || !module->append(imp))
+                return nullptr;
+            break;
+          }
           case WasmToken::Export: {
             WasmAstExport* exp = ParseExport(c);
             if (!exp || !module->append(exp))
@@ -933,7 +1010,7 @@ EncodeExpr(Encoder& e, WasmAstExpr& expr)
 static bool
 EncodeSignatureSection(Encoder& e, WasmAstModule& module)
 {
-    if (module.funcs().empty())
+    if (module.sigs().empty())
         return true;
 
     if (!e.writeCString(SigSection))
@@ -988,6 +1065,57 @@ EncodeDeclarationSection(Encoder& e, WasmAstModule& module)
     return true;
 }
 
+static bool
+EncodeImport(Encoder& e, WasmAstImport& imp)
+{
+    if (!e.writeCString(FuncSubsection))
+        return false;
+
+    if (!e.writeVarU32(imp.sigIndex()))
+        return false;
+
+    UniqueChars moduleChars(JS::CharsToNewUTF8CharsZ(nullptr, imp.module()).c_str());
+    if (!moduleChars)
+        return false;
+
+    if (!e.writeCString(moduleChars.get()))
+        return false;
+
+    UniqueChars funcChars(JS::CharsToNewUTF8CharsZ(nullptr, imp.func()).c_str());
+    if (!funcChars)
+        return false;
+
+    if (!e.writeCString(funcChars.get()))
+        return false;
+
+    return true;
+}
+
+static bool
+EncodeImportSection(Encoder& e, WasmAstModule& module)
+{
+    if (module.imports().empty())
+        return true;
+
+    if (!e.writeCString(ImportSection))
+        return false;
+
+    size_t offset;
+    if (!e.startSection(&offset))
+        return false;
+
+    if (!e.writeVarU32(module.imports().length()))
+        return false;
+
+    for (WasmAstImport* imp : module.imports()) {
+        if (!EncodeImport(e, *imp))
+            return false;
+    }
+
+    e.finishSection(offset);
+    return true;
+}
+
 static bool
 EncodeExport(Encoder& e, WasmAstExport& exp)
 {
@@ -1109,6 +1237,9 @@ AstToBinary(WasmAstModule& module)
     if (!EncodeDeclarationSection(e, module))
         return nullptr;
 
+    if (!EncodeImportSection(e, module))
+        return nullptr;
+
     if (!EncodeExportSection(e, module))
         return nullptr;
 
diff --git a/js/src/jit-test/tests/wasm/basic.js b/js/src/jit-test/tests/wasm/basic.js
index 27969eee93e5..46ad5f5b04e4 100644
--- a/js/src/jit-test/tests/wasm/basic.js
+++ b/js/src/jit-test/tests/wasm/basic.js
@@ -95,6 +95,37 @@ wasmEvalText('(module (func (param f64)))');
 assertErrorMessage(() => wasmEvalText('(module (func (param i64)))'), TypeError, /NYI/);
 assertErrorMessage(() => wasmEvalText('(module (func (result i64)))'), TypeError, /NYI/);
 
+// ----------------------------------------------------------------------------
+// imports
+
+assertErrorMessage(() => wasmEvalText('(module (import "a" "b"))', 1), Error, /Second argument, if present, must be an Object/);
+assertErrorMessage(() => wasmEvalText('(module (import "a" "b"))', null), Error, /Second argument, if present, must be an Object/);
+
+const noImportObj = /no import object given/;
+const notObject = /import object field is not an Object/;
+const notFunction = /import object field is not a Function/;
+
+var code = '(module (import "a" "b"))';
+assertErrorMessage(() => wasmEvalText(code), TypeError, noImportObj);
+assertErrorMessage(() => wasmEvalText(code, {}), TypeError, notObject);
+assertErrorMessage(() => wasmEvalText(code, {a:1}), TypeError, notObject);
+assertErrorMessage(() => wasmEvalText(code, {a:{}}), TypeError, notFunction);
+assertErrorMessage(() => wasmEvalText(code, {a:{b:1}}), TypeError, notFunction);
+wasmEvalText(code, {a:{b:()=>{}}});
+
+var code = '(module (import "" "b"))';
+assertErrorMessage(() => wasmEvalText(code), TypeError, /module name cannot be empty/);
+
+var code = '(module (import "a" ""))';
+assertErrorMessage(() => wasmEvalText(code), TypeError, noImportObj);
+assertErrorMessage(() => wasmEvalText(code, {}), TypeError, notFunction);
+assertErrorMessage(() => wasmEvalText(code, {a:1}), TypeError, notFunction);
+wasmEvalText(code, {a:()=>{}});
+
+var code = '(module (import "a" "") (import "b" "c") (import "c" ""))';
+assertErrorMessage(() => wasmEvalText(code, {a:()=>{}, b:{c:()=>{}}, c:{}}), TypeError, notFunction);
+wasmEvalText(code, {a:()=>{}, b:{c:()=>{}}, c:()=>{}});
+
 // ----------------------------------------------------------------------------
 // locals
 
diff --git a/js/src/jit-test/tests/wasm/binary.js b/js/src/jit-test/tests/wasm/binary.js
index 99cfaaaa5a3d..719b71d9d1fa 100644
--- a/js/src/jit-test/tests/wasm/binary.js
+++ b/js/src/jit-test/tests/wasm/binary.js
@@ -18,8 +18,10 @@ const ver3 = 0xff;
 // Section names
 const sigSectionStr = "sig";
 const declSectionStr = "decl";
+const importSectionStr = "import";
 const exportSectionStr = "export";
 const codeSectionStr = "code";
+const funcSubsectionStr = "func";
 
 const magicError = /failed to match magic number/;
 const versionError = /failed to match binary version/;
@@ -36,7 +38,7 @@ const B32x4Code = 6;
 const VoidCode = 7;
 
 function toBuf(array) {
-    for (var b of array)
+    for (let b of array)
         assertEq(b < 256, true);
     return Uint8Array.from(array).buffer;
 }
@@ -66,7 +68,7 @@ assertEq(Object.getOwnPropertyNames(o).length, 0);
 assertErrorMessage(() => wasmEval(toBuf(moduleHeaderThen(1))), TypeError, sectionError);
 assertErrorMessage(() => wasmEval(toBuf(moduleHeaderThen(0, 1))), TypeError, extraError);
 
-function sectionName(name) {
+function cstring(name) {
     return (name + '\0').split('').map(c => c.charCodeAt(0));
 }
 
@@ -78,8 +80,8 @@ function sectionLength(length) {
 
 function moduleWithSections(sectionArray) {
     var bytes = moduleHeaderThen();
-    for (section of sectionArray) {
-        bytes.push(...sectionName(section.name));
+    for (let section of sectionArray) {
+        bytes.push(...cstring(section.name));
         bytes.push(...sectionLength(section.body.length));
         bytes.push(...section.body);
     }
@@ -90,15 +92,53 @@ function moduleWithSections(sectionArray) {
 function sigSection(sigs) {
     var body = [];
     body.push(...varU32(sigs.length));
-    for (var sig of sigs) {
+    for (let sig of sigs) {
         body.push(...varU32(sig.args.length));
         body.push(...varU32(sig.ret));
-        for (var arg of sig.args)
+        for (let arg of sig.args)
             body.push(...varU32(arg));
     }
     return { name: sigSectionStr, body };
 }
 
+function declSection(decls) {
+    var body = [];
+    body.push(...varU32(decls.length));
+    for (let decl of decls)
+        body.push(...varU32(decl));
+    return { name: declSectionStr, body };
+}
+
+function codeSection(funcs) {
+    var body = [];
+    body.push(...varU32(funcs.length));
+    for (let func of funcs) {
+        body.push(...cstring(funcSubsectionStr));
+        var locals = varU32(func.locals.length);
+        for (let local of func.locals)
+            locals.push(...varU32(local));
+        body.push(...sectionLength(locals.length + func.body.length));
+        body = body.concat(locals, func.body);
+    }
+    return { name: codeSectionStr, body };
+}
+
+function importSection(imports) {
+    var body = [];
+    body.push(...varU32(imports.length));
+    for (let imp of imports) {
+        body.push(...cstring(funcSubsectionStr));
+        body.push(...varU32(imp.sigIndex));
+        body.push(...cstring(imp.module));
+        body.push(...cstring(imp.func));
+    }
+    return { name: importSectionStr, body };
+}
+
+const trivialSigSection = sigSection([{args:[], ret:VoidCode}]);
+const trivialDeclSection = declSection([0]);
+const trivialCodeSection = codeSection([{locals:[], body:[0, 0]}]);
+
 assertThrowsInstanceOf(() => wasmEval(toBuf(moduleWithSections([{name: sigSectionStr, body: [1]}]))), TypeError);
 assertThrowsInstanceOf(() => wasmEval(toBuf(moduleWithSections([{name: sigSectionStr, body: [1, 1, 0]}]))), TypeError);
 
@@ -109,15 +149,13 @@ wasmEval(toBuf(moduleWithSections([sigSection([{args:[I32Code], ret:VoidCode}])]
 assertErrorMessage(() => wasmEval(toBuf(moduleWithSections([sigSection([{args:[], ret:100}])]))), TypeError, /bad expression type/);
 assertErrorMessage(() => wasmEval(toBuf(moduleWithSections([sigSection([{args:[100], ret:VoidCode}])]))), TypeError, /bad value type/);
 
-function declSection(decls) {
-    var body = [];
-    body.push(...varU32(decls.length));
-    for (var decl of decls)
-        body.push(...varU32(decl));
-    return { name: declSectionStr, body };
-}
-
 assertThrowsInstanceOf(() => wasmEval(toBuf(moduleWithSections([sigSection([]), declSection([0])]))), TypeError, /signature index out of range/);
-assertThrowsInstanceOf(() => wasmEval(toBuf(moduleWithSections([sigSection([{args:[], ret:VoidCode}]), declSection([1])]))), TypeError, /signature index out of range/);
+assertThrowsInstanceOf(() => wasmEval(toBuf(moduleWithSections([trivialSigSection, declSection([1])]))), TypeError, /signature index out of range/);
+assertErrorMessage(() => wasmEval(toBuf(moduleWithSections([trivialSigSection, declSection([0])]))), TypeError, /fewer function definitions than declarations/);
+wasmEval(toBuf(moduleWithSections([trivialSigSection, trivialDeclSection, trivialCodeSection])));
 
-assertErrorMessage(() => wasmEval(toBuf(moduleWithSections([sigSection([{args:[], ret:VoidCode}]), declSection([0])]))), TypeError, /fewer function definitions than declarations/);
+assertThrowsInstanceOf(() => wasmEval(toBuf(moduleWithSections([trivialSigSection, {name: importSectionStr, body:[]}]))), TypeError);
+assertErrorMessage(() => wasmEval(toBuf(moduleWithSections([importSection([{sigIndex:0, module:"a", func:"b"}])]))), TypeError, /signature index out of range/);
+assertErrorMessage(() => wasmEval(toBuf(moduleWithSections([trivialSigSection, importSection([{sigIndex:1, module:"a", func:"b"}])]))), TypeError, /signature index out of range/);
+wasmEval(toBuf(moduleWithSections([trivialSigSection, importSection([])])));
+wasmEval(toBuf(moduleWithSections([trivialSigSection, importSection([{sigIndex:0, module:"a", func:""}])])), {a:()=>{}});