diff --git a/js/src/frontend/SharedContext.cpp b/js/src/frontend/SharedContext.cpp
index 5ee4a7c7f5c7..83e16b6fb61d 100644
--- a/js/src/frontend/SharedContext.cpp
+++ b/js/src/frontend/SharedContext.cpp
@@ -24,7 +24,6 @@ SharedContext::SharedContext(JSContext* cx, Kind kind,
                              Directives directives, SourceExtent extent,
                              ImmutableScriptFlags immutableFlags)
     : cx_(cx),
-      kind_(kind),
       compilationInfo_(compilationInfo),
       thisBinding_(ThisBinding::Global),
       extent(extent),
@@ -37,15 +36,15 @@ SharedContext::SharedContext(JSContext* cx, Kind kind,
       localStrict(false),
       hasExplicitUseStrict_(false),
       immutableFlags_(immutableFlags) {
-  if (kind_ == Kind::FunctionBox) {
+  if (kind == Kind::FunctionBox) {
     immutableFlags_.setFlag(ImmutableFlags::IsFunction);
-  } else if (kind_ == Kind::Module) {
+  } else if (kind == Kind::Module) {
     MOZ_ASSERT(!compilationInfo.options.nonSyntacticScope);
     immutableFlags_.setFlag(ImmutableFlags::IsModule);
-  } else if (kind_ == Kind::Eval) {
+  } else if (kind == Kind::Eval) {
     immutableFlags_.setFlag(ImmutableFlags::IsForEval);
   } else {
-    MOZ_ASSERT(kind_ == Kind::Global);
+    MOZ_ASSERT(kind == Kind::Global);
   }
 
   immutableFlags_.setFlag(ImmutableFlags::Strict, directives.strict());
diff --git a/js/src/frontend/SharedContext.h b/js/src/frontend/SharedContext.h
index 2f4ff63e3634..79224b228c0d 100644
--- a/js/src/frontend/SharedContext.h
+++ b/js/src/frontend/SharedContext.h
@@ -110,8 +110,6 @@ class SharedContext {
  protected:
   enum class Kind : uint8_t { FunctionBox, Global, Eval, Module };
 
-  Kind kind_;
-
   CompilationInfo& compilationInfo_;
 
   ThisBinding thisBinding_;
@@ -156,25 +154,29 @@ class SharedContext {
   // it. Otherwise nullptr.
   virtual Scope* compilationEnclosingScope() const = 0;
 
-  bool isFunctionBox() const { return kind_ == Kind::FunctionBox; }
+  bool isFunctionBox() const {
+    return immutableFlags_.hasFlag(ImmutableFlags::IsFunction);
+  }
   inline FunctionBox* asFunctionBox();
-  bool isModuleContext() const { return kind_ == Kind::Module; }
+  bool isModuleContext() const {
+    return immutableFlags_.hasFlag(ImmutableFlags::IsModule);
+  }
   inline ModuleSharedContext* asModuleContext();
-  bool isGlobalContext() const { return kind_ == Kind::Global; }
+  bool isGlobalContext() const {
+    return !(isFunctionBox() || isModuleContext() || isEvalContext());
+  }
   inline GlobalSharedContext* asGlobalContext();
-  bool isEvalContext() const { return kind_ == Kind::Eval; }
+  bool isEvalContext() const {
+    return immutableFlags_.hasFlag(ImmutableFlags::IsForEval);
+  }
   inline EvalSharedContext* asEvalContext();
 
   bool isTopLevelContext() const {
-    switch (kind_) {
-      case Kind::Module:
-      case Kind::Global:
-      case Kind::Eval:
-        return true;
-      case Kind::FunctionBox:
-        break;
+    if (isModuleContext() || isEvalContext() || isGlobalContext()) {
+      return true;
     }
-    MOZ_ASSERT(kind_ == Kind::FunctionBox);
+
+    MOZ_ASSERT(isFunctionBox());
     return false;
   }