--- a/js/src/jit/MIR.h
+++ b/js/src/jit/MIR.h
@@ -12630,16 +12630,20 @@ class MAsmJSLoadHeap
 
     MDefinition *ptr() const { return getOperand(0); }
     void replacePtr(MDefinition *newPtr) { replaceOperand(0, newPtr); }
     MemoryBarrierBits barrierBefore() const { return barrierBefore_; }
     MemoryBarrierBits barrierAfter() const { return barrierAfter_; }
 
     bool congruentTo(const MDefinition *ins) const override;
     AliasSet getAliasSet() const override {
+        // When a barrier is needed make the instruction effectful by
+        // giving it a "store" effect.
+        if (barrierBefore_|barrierAfter_)
+            return AliasSet::Store(AliasSet::AsmJSHeap);
         return AliasSet::Load(AliasSet::AsmJSHeap);
     }
     bool mightAlias(const MDefinition *def) const override;
 };
 
 class MAsmJSStoreHeap
   : public MBinaryInstruction,
     public MAsmJSHeapAccess,