diff --git a/js/src/wasm/WasmJS.cpp b/js/src/wasm/WasmJS.cpp
index c871ec964367..1d07b0d065fe 100644
--- a/js/src/wasm/WasmJS.cpp
+++ b/js/src/wasm/WasmJS.cpp
@@ -1022,7 +1022,7 @@ WasmInstanceObject::create(JSContext* cx,
         return nullptr;
     }
 
-    UniquePtr<WeakScopeMap> scopes = js::MakeUnique<WeakScopeMap>(cx->zone());
+    UniquePtr<ScopeMap> scopes = js::MakeUnique<ScopeMap>(cx->zone());
     if (!scopes || !scopes->init()) {
         ReportOutOfMemory(cx);
         return nullptr;
@@ -1143,10 +1143,10 @@ WasmInstanceObject::exports() const
     return *(ExportMap*)getReservedSlot(EXPORTS_SLOT).toPrivate();
 }
 
-WasmInstanceObject::WeakScopeMap&
+WasmInstanceObject::ScopeMap&
 WasmInstanceObject::scopes() const
 {
-    return *(WeakScopeMap*)getReservedSlot(SCOPES_SLOT).toPrivate();
+    return *(ScopeMap*)getReservedSlot(SCOPES_SLOT).toPrivate();
 }
 
 static bool
@@ -1440,18 +1440,18 @@ WasmMemoryObject::hasObservers() const
     return !getReservedSlot(OBSERVERS_SLOT).isUndefined();
 }
 
-WasmMemoryObject::WeakInstanceSet&
+WasmMemoryObject::InstanceSet&
 WasmMemoryObject::observers() const
 {
     MOZ_ASSERT(hasObservers());
-    return *reinterpret_cast<WeakInstanceSet*>(getReservedSlot(OBSERVERS_SLOT).toPrivate());
+    return *reinterpret_cast<InstanceSet*>(getReservedSlot(OBSERVERS_SLOT).toPrivate());
 }
 
-WasmMemoryObject::WeakInstanceSet*
+WasmMemoryObject::InstanceSet*
 WasmMemoryObject::getOrCreateObservers(JSContext* cx)
 {
     if (!hasObservers()) {
-        auto observers = MakeUnique<WeakInstanceSet>(cx->zone());
+        auto observers = MakeUnique<InstanceSet>(cx->zone());
         if (!observers || !observers->init()) {
             ReportOutOfMemory(cx);
             return nullptr;
@@ -1478,7 +1478,7 @@ WasmMemoryObject::addMovingGrowObserver(JSContext* cx, WasmInstanceObject* insta
 {
     MOZ_ASSERT(movingGrowable());
 
-    WeakInstanceSet* observers = getOrCreateObservers(cx);
+    InstanceSet* observers = getOrCreateObservers(cx);
     if (!observers)
         return false;
 
diff --git a/js/src/wasm/WasmJS.h b/js/src/wasm/WasmJS.h
index b6925132caad..8cacb6752d32 100644
--- a/js/src/wasm/WasmJS.h
+++ b/js/src/wasm/WasmJS.h
@@ -167,12 +167,11 @@ class WasmInstanceObject : public NativeObject
     // WeakScopeMap maps from function index to js::Scope. This maps is weak
     // to avoid holding scope objects alive. The scopes are normally created
     // during debugging.
-    using ScopeMap = GCHashMap<uint32_t,
-                               ReadBarriered<WasmFunctionScope*>,
-                               DefaultHasher<uint32_t>,
-                               SystemAllocPolicy>;
-    using WeakScopeMap = JS::WeakCache<ScopeMap>;
-    WeakScopeMap& scopes() const;
+    using ScopeMap = JS::WeakCache<GCHashMap<uint32_t,
+                                             ReadBarriered<WasmFunctionScope*>,
+                                             DefaultHasher<uint32_t>,
+                                             SystemAllocPolicy>>;
+    ScopeMap& scopes() const;
 
   public:
     static const unsigned RESERVED_SLOTS = 4;
@@ -222,13 +221,12 @@ class WasmMemoryObject : public NativeObject
     static bool growImpl(JSContext* cx, const CallArgs& args);
     static bool grow(JSContext* cx, unsigned argc, Value* vp);
 
-    using InstanceSet = GCHashSet<ReadBarrieredWasmInstanceObject,
-                                  MovableCellHasher<ReadBarrieredWasmInstanceObject>,
-                                  SystemAllocPolicy>;
-    using WeakInstanceSet = JS::WeakCache<InstanceSet>;
+    using InstanceSet = JS::WeakCache<GCHashSet<ReadBarrieredWasmInstanceObject,
+                                                MovableCellHasher<ReadBarrieredWasmInstanceObject>,
+                                                SystemAllocPolicy>>;
     bool hasObservers() const;
-    WeakInstanceSet& observers() const;
-    WeakInstanceSet* getOrCreateObservers(JSContext* cx);
+    InstanceSet& observers() const;
+    InstanceSet* getOrCreateObservers(JSContext* cx);
 
   public:
     static const unsigned RESERVED_SLOTS = 2;
diff --git a/js/src/wasm/WasmTable.h b/js/src/wasm/WasmTable.h
index 6c955fc72d5c..64369386ca1a 100644
--- a/js/src/wasm/WasmTable.h
+++ b/js/src/wasm/WasmTable.h
@@ -31,13 +31,13 @@ namespace wasm {
 
 class Table : public ShareableBase<Table>
 {
-    using InstanceSet = GCHashSet<ReadBarrieredWasmInstanceObject,
-                                  MovableCellHasher<ReadBarrieredWasmInstanceObject>,
-                                  SystemAllocPolicy>;
-    typedef UniquePtr<uint8_t[], JS::FreePolicy> UniqueByteArray;
+    using InstanceSet = JS::WeakCache<GCHashSet<ReadBarrieredWasmInstanceObject,
+                                                MovableCellHasher<ReadBarrieredWasmInstanceObject>,
+                                                SystemAllocPolicy>>;
+    using UniqueByteArray = UniquePtr<uint8_t[], JS::FreePolicy>;
 
     ReadBarrieredWasmTableObject maybeObject_;
-    JS::WeakCache<InstanceSet>   observers_;
+    InstanceSet                  observers_;
     UniqueByteArray              array_;
     const TableKind              kind_;
     uint32_t                     length_;