diff --git a/src/crankshaft/x87/lithium-codegen-x87.cc b/src/crankshaft/x87/lithium-codegen-x87.cc
index d2c829398f..62690376f5 100644
--- a/src/crankshaft/x87/lithium-codegen-x87.cc
+++ b/src/crankshaft/x87/lithium-codegen-x87.cc
@@ -2520,11 +2520,12 @@ void LCodeGen::EmitClassOfTest(Label* is_true,
   DCHECK(!temp.is(temp2));
   __ JumpIfSmi(input, is_false);
 
-  __ CmpObjectType(input, JS_FUNCTION_TYPE, temp);
+  __ CmpObjectType(input, FIRST_FUNCTION_TYPE, temp);
+  STATIC_ASSERT(LAST_FUNCTION_TYPE == LAST_TYPE);
   if (String::Equals(isolate()->factory()->Function_string(), class_name)) {
-    __ j(equal, is_true);
+    __ j(above_equal, is_true);
   } else {
-    __ j(equal, is_false);
+    __ j(above_equal, is_false);
   }
 
   // Now we are in the FIRST-LAST_NONCALLABLE_SPEC_OBJECT_TYPE range.
diff --git a/src/full-codegen/x87/full-codegen-x87.cc b/src/full-codegen/x87/full-codegen-x87.cc
index 753db70d54..c21a53ad3c 100644
--- a/src/full-codegen/x87/full-codegen-x87.cc
+++ b/src/full-codegen/x87/full-codegen-x87.cc
@@ -2715,9 +2715,10 @@ void FullCodeGenerator::EmitClassOf(CallRuntime* expr) {
   __ CmpObjectType(eax, FIRST_JS_RECEIVER_TYPE, eax);
   __ j(below, &null, Label::kNear);
 
-  // Return 'Function' for JSFunction objects.
-  __ CmpInstanceType(eax, JS_FUNCTION_TYPE);
-  __ j(equal, &function, Label::kNear);
+  // Return 'Function' for JSFunction and JSBoundFunction objects.
+  __ CmpInstanceType(eax, FIRST_FUNCTION_TYPE);
+  STATIC_ASSERT(LAST_FUNCTION_TYPE == LAST_TYPE);
+  __ j(above_equal, &function, Label::kNear);
 
   // Check if the constructor in the map is a JS function.
   __ GetMapConstructor(eax, eax, ebx);