diff --git a/mozilla/js/src/jsiter.c b/mozilla/js/src/jsiter.c
index 987e9cab465..9d09ad48487 100644
--- a/mozilla/js/src/jsiter.c
+++ b/mozilla/js/src/jsiter.c
@@ -829,6 +829,13 @@ SendToGenerator(JSContext *cx, JSGeneratorOp op, JSObject *obj,
     JSArena *arena;
     JSBool ok;
 
+    if (gen->state == JSGEN_RUNNING || gen->state == JSGEN_CLOSING) {
+        js_ReportValueError(cx, JSMSG_NESTING_GENERATOR,
+                            JSDVG_SEARCH_STACK, OBJECT_TO_JSVAL(obj),
+                            JS_GetFunctionId(gen->frame.fun));
+        return JS_FALSE;
+    }
+
     JS_ASSERT(gen->state ==  JSGEN_NEWBORN || gen->state == JSGEN_OPEN);
     switch (op) {
       case JSGENOP_NEXT:
@@ -917,7 +924,6 @@ CloseGenerator(JSContext *cx, JSObject *obj)
         return JS_TRUE;
     }
 
-    JS_ASSERT(gen->state != JSGEN_RUNNING && gen->state != JSGEN_CLOSING);
     if (gen->state == JSGEN_CLOSED)
         return JS_TRUE;
 
@@ -944,8 +950,7 @@ generator_op(JSContext *cx, JSGeneratorOp op,
         goto closed_generator;
     }
 
-    switch (gen->state) {
-      case JSGEN_NEWBORN:
+    if (gen->state == JSGEN_NEWBORN) {
         switch (op) {
           case JSGENOP_NEXT:
           case JSGENOP_THROW:
@@ -964,21 +969,7 @@ generator_op(JSContext *cx, JSGeneratorOp op,
             gen->state = JSGEN_CLOSED;
             return JS_TRUE;
         }
-        break;
-
-      case JSGEN_OPEN:
-        break;
-
-      case JSGEN_RUNNING:
-      case JSGEN_CLOSING:
-        js_ReportValueError(cx, JSMSG_NESTING_GENERATOR,
-                            JSDVG_SEARCH_STACK, argv[-1],
-                            JS_GetFunctionId(gen->frame.fun));
-        return JS_FALSE;
-
-      default:
-        JS_ASSERT(gen->state == JSGEN_CLOSED);
-
+    } else if (gen->state == JSGEN_CLOSED) {
       closed_generator:
         switch (op) {
           case JSGENOP_NEXT: