diff --git a/js/src/jit-test/tests/basic/bug631082.js b/js/src/jit-test/tests/basic/bug631082.js
new file mode 100644
index 000000000000..61db35a57bdd
--- /dev/null
+++ b/js/src/jit-test/tests/basic/bug631082.js
@@ -0,0 +1,13 @@
+var t;
+(function () {
+    t = (function() {
+            yield k();
+        })();
+    function h() {
+    }
+    function k() {
+        return function() { h(); };
+    }
+})();
+t.next();
+
diff --git a/js/src/jsparse.cpp b/js/src/jsparse.cpp
index 302f150179aa..b63d008822dc 100644
--- a/js/src/jsparse.cpp
+++ b/js/src/jsparse.cpp
@@ -2092,8 +2092,15 @@ FindFunArgs(JSFunctionBox *funbox, int level, JSFunctionBoxQueue *queue)
          * TCF_FUN_HEAVYWEIGHT bottom up, funbox's ancestor function nodes have
          * already been marked as funargs by this point. Therefore we have to
          * flag only funbox->node and funbox->kids' nodes here.
+         *
+         * Generators need to be treated in the same way. Even if the value
+         * of a generator function doesn't escape, anything defined or referred
+         * to inside the generator can escape through a call to the generator.
+         * We could imagine doing static analysis to track the calls and see
+         * if any iterators or values returned by iterators escape, but that
+         * would be hard, so instead we just assume everything might escape.
          */
-        if (funbox->tcflags & TCF_FUN_HEAVYWEIGHT) {
+        if (funbox->tcflags & (TCF_FUN_HEAVYWEIGHT | TCF_FUN_IS_GENERATOR)) {
             fn->setFunArg();
             for (JSFunctionBox *kid = funbox->kids; kid; kid = kid->siblings)
                 kid->node->setFunArg();