--- a/js/src/jsparse.cpp
+++ b/js/src/jsparse.cpp
@@ -6511,18 +6511,18 @@ js_FoldConstants(JSContext *cx, JSParseN
                         RecycleTree(pn1, tc);
                         --pn->pn_count;
                     } else {
                         pnp = &pn1->pn_next;
                     }
                 } while ((pn1 = *pnp) != NULL);
 
                 // We may have to change arity from LIST to BINARY.
+                pn1 = pn->pn_head;
                 if (pn->pn_count == 2) {
-                    pn1 = pn->pn_head;
                     pn2 = pn1->pn_next;
                     pn1->pn_next = NULL;
                     JS_ASSERT(!pn2->pn_next);
                     pn->pn_arity = PN_BINARY;
                     pn->pn_left = pn1;
                     pn->pn_right = pn2;
                 } else if (pn->pn_count == 1) {
                     PN_MOVE_NODE(pn, pn1);