diff --git a/hphp/runtime/base/tv_helpers.h b/hphp/runtime/base/tv_helpers.h
index ec8ec9e68..d0f2315d7 100644
--- a/hphp/runtime/base/tv_helpers.h
+++ b/hphp/runtime/base/tv_helpers.h
@@ -203,7 +203,7 @@ inline void cellCopy(const Cell& fr, Cell& to) {
   tvCopy(fr, to);
 }
 inline void varCopy(const Var& fr, Var& to) {
-  assert(cellIsPlausible(&fr));
+  assert(varIsPlausible(&fr));
   tvCopy(fr, to);
 }