diff --git a/js/src/jsdbgapi.cpp b/js/src/jsdbgapi.cpp
index 62345324602b..b20467f4b0b8 100644
--- a/js/src/jsdbgapi.cpp
+++ b/js/src/jsdbgapi.cpp
@@ -60,6 +60,7 @@
 #include "jsparse.h"
 #include "jsscope.h"
 #include "jsscript.h"
+#include "jsstaticcheck.h"
 #include "jsstr.h"
 
 #include "jsautooplen.h"
@@ -1241,6 +1242,9 @@ JS_EvaluateUCInStackFrame(JSContext *cx, JSStackFrame *fp,
                           const char *filename, uintN lineno,
                           jsval *rval)
 {
+    JS_ASSERT(cx->fp);
+    JS_ASSERT_NOT_ON_TRACE(cx);
+
     JSObject *scobj;
     JSScript *script;
     JSBool ok;