diff --git a/js/src/jsiter.c b/js/src/jsiter.c
index 2c13d298a441..7c2982060974 100644
--- a/js/src/jsiter.c
+++ b/js/src/jsiter.c
@@ -76,6 +76,33 @@ extern const char js_throw_str[]; /* from jsscan.h */
 #error JS_INITIAL_NSLOTS must be greater than JSSLOT_ITER_FLAGS.
 #endif
 
+static uint32
+iterator_mark(JSContext *cx, JSObject *obj, void *arg)
+{
+    jsval state, parent;
+    JSObject *iterable;
+
+    /* Avoid double work if js_CloseNativeIterator was called on obj. */
+    state = obj->slots[JSSLOT_ITER_STATE];
+    if (JSVAL_IS_VOID(state))
+        return 0;
+
+    parent = obj->slots[JSSLOT_PARENT];
+    if (!JSVAL_IS_NULL(state) && !JSVAL_IS_PRIMITIVE(parent)) {
+        iterable = JSVAL_TO_OBJECT(parent);
+#if JS_HAS_XML_SUPPORT
+        if ((JSVAL_TO_INT(obj->slots[JSSLOT_ITER_FLAGS]) & JSITER_FOREACH) &&
+            OBJECT_IS_XML(cx, iterable)) {
+            ((JSXMLObjectOps *) iterable->map->ops)->
+                enumerateValues(cx, iterable, JSENUMERATE_MARK, &state,
+                                NULL, NULL);
+        } else
+#endif
+            OBJ_ENUMERATE(cx, iterable, JSENUMERATE_MARK, &state, NULL);
+    }
+    return 0;
+}
+
 static void
 iterator_close(JSContext *cx, JSObject *obj)
 {
@@ -110,7 +137,8 @@ JSExtendedClass js_IteratorClass = {
     JSCLASS_HAS_CACHED_PROTO(JSProto_Iterator),
     JS_PropertyStub,  JS_PropertyStub,  JS_PropertyStub,  JS_PropertyStub,
     JS_EnumerateStub, JS_ResolveStub,   JS_ConvertStub,   JS_FinalizeStub,
-    JSCLASS_NO_OPTIONAL_MEMBERS },
+    NULL,             NULL,             NULL,             NULL,
+    NULL,             NULL,             iterator_mark,    NULL },
     NULL,             NULL,             NULL,             iterator_close,
     JSCLASS_NO_RESERVED_MEMBERS
 };
diff --git a/js/src/jsobj.c b/js/src/jsobj.c
index e658b5feaf05..aa94cdd9dbfa 100644
--- a/js/src/jsobj.c
+++ b/js/src/jsobj.c
@@ -3793,6 +3793,22 @@ js_Enumerate(JSContext *cx, JSObject *obj, JSIterateOp enum_op,
         JS_free(cx, state);
         *statep = JSVAL_NULL;
         break;
+
+      case JSENUMERATE_MARK:
+        state = (JSNativeIteratorState *) JSVAL_TO_PRIVATE(*statep);
+        ida = state->ida;
+        length = ida->length;
+        for (i = 0; i < length; i++) {
+            jsid id;
+
+            id = ida->vector[i];
+            if (JSID_IS_ATOM(id)) {
+                GC_MARK_ATOM(cx, JSID_TO_ATOM(id));
+            } else if (JSID_IS_OBJECT(id)) {
+                GC_MARK(cx, JSID_TO_OBJECT(id), "ida->vector[i]");
+            }
+        }
+        break;
     }
     return JS_TRUE;
 }
diff --git a/js/src/jspubtd.h b/js/src/jspubtd.h
index e6e0871c2cd8..6fb0abd19647 100644
--- a/js/src/jspubtd.h
+++ b/js/src/jspubtd.h
@@ -119,7 +119,8 @@ typedef enum JSAccessMode {
 typedef enum JSIterateOp {
     JSENUMERATE_INIT,       /* Create new iterator state */
     JSENUMERATE_NEXT,       /* Iterate once */
-    JSENUMERATE_DESTROY     /* Destroy iterator state */
+    JSENUMERATE_DESTROY,    /* Destroy iterator state */
+    JSENUMERATE_MARK        /* mark opaque iterator state */
 } JSIterateOp;
 
 /* Struct typedefs. */
diff --git a/js/src/jsxml.c b/js/src/jsxml.c
index ff97665f4770..868f8efa0a19 100644
--- a/js/src/jsxml.c
+++ b/js/src/jsxml.c
@@ -5151,6 +5151,9 @@ xml_enumerate(JSContext *cx, JSObject *obj, JSIterateOp enum_op,
         }
         *statep = JSVAL_NULL;
         break;
+
+      case JSENUMERATE_MARK:
+        break;
     }
     return JS_TRUE;
 }
@@ -5310,6 +5313,9 @@ xml_enumerateValues(JSContext *cx, JSObject *obj, JSIterateOp enum_op,
         }
         *statep = JSVAL_NULL;
         break;
+
+      case JSENUMERATE_MARK:
+        break;
     }
     return JS_TRUE;
 }