diff --git a/js/src/jsbuiltins.cpp b/js/src/jsbuiltins.cpp
index 666f215ca9c..e1a00ea7cbc 100644
--- a/js/src/jsbuiltins.cpp
+++ b/js/src/jsbuiltins.cpp
@@ -403,6 +403,8 @@ js_PopInterpFrame(JSContext* cx, InterpState* state)
         return JS_FALSE;
     if (cx->fp->imacpc)
         return JS_FALSE;
+    if (cx->fp->blockChain)
+        return JS_FALSE;
 
     cx->fp->putActivationObjects(cx);
     
diff --git a/js/src/jsrecursion.cpp b/js/src/jsrecursion.cpp
index b3a13c51674..e3f51fe28ce 100644
--- a/js/src/jsrecursion.cpp
+++ b/js/src/jsrecursion.cpp
@@ -226,7 +226,7 @@ TraceRecorder::upRecursion()
     unsigned totalSlots = NativeStackSlots(cx, 1);
     unsigned downPostSlots = totalSlots - NativeStackSlots(cx, 0);
     FrameInfo* fi = (FrameInfo*)alloca(sizeof(FrameInfo) + totalSlots * sizeof(TraceType));
-    fi->block = cx->fp->down->blockChain;
+    fi->block = NULL;
     fi->pc = (jsbytecode*)return_pc;
     fi->imacpc = NULL;
 
diff --git a/js/src/jstracer.cpp b/js/src/jstracer.cpp
index e3612a9c93e..096222b843e 100644
--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -9723,6 +9723,8 @@ IsTraceableRecursion(JSContext *cx)
         return false;
     if ((fp->flags & JSFRAME_CONSTRUCTING) || (down->flags & JSFRAME_CONSTRUCTING))
         return false;
+    if (fp->blockChain || down->blockChain)
+        return false;
     if (*fp->script->code != JSOP_TRACE)
         return false;
     return true;