diff --git a/js/src/jstracer.cpp b/js/src/jstracer.cpp
index 1bed89c3d6a5..bf95a453eb51 100644
--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -5029,6 +5029,9 @@ TraceRecorder::tableswitch()
     if (v_ins->isconst() || v_ins->isconstq())
         return NULL;
 
+    if (!isNumber(v))
+        return NULL;
+
     jsbytecode* pc = cx->fp->regs->pc;
     /* Starting a new trace after exiting a trace via switch. */
     if (anchor && (anchor->exitType == CASE_EXIT ||