diff --git a/js/src/jit/BaselineIC.cpp b/js/src/jit/BaselineIC.cpp
index 6752dfce36f..dff10348611 100644
--- a/js/src/jit/BaselineIC.cpp
+++ b/js/src/jit/BaselineIC.cpp
@@ -1969,6 +1969,8 @@ DoCompareFallback(JSContext *cx, BaselineFrame *frame, ICCompare_Fallback *stub_
         }
     }
 
+    stub->noteUnoptimizableAccess();
+
     return true;
 }
 
diff --git a/js/src/jit/BaselineIC.h b/js/src/jit/BaselineIC.h
index d628986af4d..975a56987c3 100644
--- a/js/src/jit/BaselineIC.h
+++ b/js/src/jit/BaselineIC.h
@@ -1966,6 +1966,14 @@ class ICCompare_Fallback : public ICFallbackStub
         return space->allocate<ICCompare_Fallback>(code);
     }
 
+    static const size_t UNOPTIMIZABLE_ACCESS_BIT = 0;
+    void noteUnoptimizableAccess() {
+        extra_ |= (1u << UNOPTIMIZABLE_ACCESS_BIT);
+    }
+    bool hadUnoptimizableAccess() const {
+        return extra_ & (1u << UNOPTIMIZABLE_ACCESS_BIT);
+    }
+
     // Compiler for this stub kind.
     class Compiler : public ICStubCompiler {
       protected:
diff --git a/js/src/jit/BaselineInspector.cpp b/js/src/jit/BaselineInspector.cpp
index c35ba78e513..3676ff9f486 100644
--- a/js/src/jit/BaselineInspector.cpp
+++ b/js/src/jit/BaselineInspector.cpp
@@ -226,6 +226,12 @@ BaselineInspector::expectedCompareType(jsbytecode *pc)
     if (!first && !dimorphicStub(pc, &first, &second))
         return MCompare::Compare_Unknown;
 
+    if (ICStub *fallback = second ? second->next() : first->next()) {
+        JS_ASSERT(fallback->isFallback());
+        if (fallback->toCompare_Fallback()->hadUnoptimizableAccess())
+            return MCompare::Compare_Unknown;
+    }
+
     if (CanUseInt32Compare(first->kind()) && (!second || CanUseInt32Compare(second->kind()))) {
         ICCompare_Int32WithBoolean *coerce =
             first->isCompare_Int32WithBoolean()