--- a/js/src/jsobjinlines.h
+++ b/js/src/jsobjinlines.h
@@ -338,24 +338,24 @@ JSObject::slotsAndStructSize(uint32 nslo
     return sizeof(js::Value) * (ndslots + nfslots)
            + (isFun ? sizeof(JSFunction) : sizeof(JSObject));
 }
 
 inline uint32
 JSObject::getArrayLength() const
 {
     JS_ASSERT(isArray());
-    return (uint32)(size_t) getPrivate();
+    return (uint32)(uintptr_t) getPrivate();
 }
 
 inline void
 JSObject::setArrayLength(uint32 length)
 {
     JS_ASSERT(isArray());
-    setPrivate((void*)(size_t)length);
+    setPrivate((void*)(uintptr_t) length);
 }
 
 inline uint32
 JSObject::getDenseArrayCapacity()
 {
     JS_ASSERT(isDenseArray());
     return numSlots();
 }