diff --git a/js/src/ion/CompilerRoot.h b/js/src/ion/CompilerRoot.h
index 21428d1f631..6a5382d5db4 100644
--- a/js/src/ion/CompilerRoot.h
+++ b/js/src/ion/CompilerRoot.h
@@ -21,10 +21,6 @@ template <typename T>
 class CompilerRoot : public CompilerRootNode
 {
   public:
-    CompilerRoot()
-      : CompilerRootNode(NULL)
-    { }
-
     CompilerRoot(T ptr)
       : CompilerRootNode(NULL)
     {
@@ -46,6 +42,11 @@ class CompilerRoot : public CompilerRootNode
   public:
     operator T () const { return static_cast<T>(ptr); }
     T operator ->() const { return static_cast<T>(ptr); }
+
+  private:
+    CompilerRoot() MOZ_DELETE;
+    CompilerRoot(const CompilerRoot<T> &) MOZ_DELETE;
+    CompilerRoot<T> &operator =(const CompilerRoot<T> &) MOZ_DELETE;
 };
 
 typedef CompilerRoot<JSObject*>   CompilerRootObject;
diff --git a/js/src/ion/MIR.h b/js/src/ion/MIR.h
index b216ea43581..63895a1b808 100644
--- a/js/src/ion/MIR.h
+++ b/js/src/ion/MIR.h
@@ -5254,9 +5254,9 @@ class MInstanceOf
 
   public:
     MInstanceOf(MDefinition *obj, RawObject proto)
-      : MUnaryInstruction(obj)
+      : MUnaryInstruction(obj),
+        protoObj_(proto)
     {
-        protoObj_ = proto;
         setResultType(MIRType_Boolean);
     }
 
diff --git a/js/src/jit-test/tests/basic/bug815652.js b/js/src/jit-test/tests/basic/bug815652.js
new file mode 100644
index 00000000000..54297d12b76
--- /dev/null
+++ b/js/src/jit-test/tests/basic/bug815652.js
@@ -0,0 +1,10 @@
+
+gczeal(9, 2)
+function testScatterConflict() {
+  var p = new ParallelArray([1,2,3,4,5]);
+  var r = p.scatter([0,1,0,3,(0)], 9, function (a,b) { return a+b; });
+  function assertEqParallelArray(a, b)
+    assertEq(a instanceof ParallelArray, true);
+  assertEqParallelArray(r, new ParallelArray([4,2,(false),4,5]));
+}
+testScatterConflict();