diff --git a/js/src/jit-test/tests/jaeger/bug647785.js b/js/src/jit-test/tests/jaeger/bug647785.js
new file mode 100644
index 00000000000..8c53e3f8da4
--- /dev/null
+++ b/js/src/jit-test/tests/jaeger/bug647785.js
@@ -0,0 +1,4 @@
+assertEq(-(!Int32Array(5)), -0);
+assertEq(-(!Math), -0);
+assertEq(-(!{}), -0);
+assertEq(-(![]), -0);
diff --git a/js/src/methodjit/FastOps.cpp b/js/src/methodjit/FastOps.cpp
index 46c75ff555c..85a6b99f938 100644
--- a/js/src/methodjit/FastOps.cpp
+++ b/js/src/methodjit/FastOps.cpp
@@ -617,8 +617,11 @@ mjit::Compiler::jsop_not()
 
           case JSVAL_TYPE_OBJECT:
           {
+            RegisterID reg = frame.allocReg();
+            masm.move(Imm32(0), reg);
+
             frame.pop();
-            frame.push(BooleanValue(false));
+            frame.pushTypedPayload(JSVAL_TYPE_BOOLEAN, reg);
             break;
           }