diff --git a/js/src/jstracer.cpp b/js/src/jstracer.cpp
index cac3a68f058..3d35a04d0bc 100644
--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -3297,8 +3297,10 @@ TraceRecorder::record_JSOP_RETURN()
     jsval& rval = stackval(-1);
     JSStackFrame *fp = cx->fp;
     if (cx->fp->flags & JSFRAME_CONSTRUCTING) {
-        JS_ASSERT(OBJECT_TO_JSVAL(fp->thisp) == fp->argv[-1]);
-        rval_ins = get(&fp->argv[-1]);
+        if (JSVAL_IS_PRIMITIVE(rval)) {
+            JS_ASSERT(OBJECT_TO_JSVAL(fp->thisp) == fp->argv[-1]);
+            rval_ins = get(&fp->argv[-1]);
+        }
     } else {
         rval_ins = get(&rval);
     }