diff --git a/src/eval.c b/src/eval.c
index 014905ce6df..16c36fa284c 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -831,6 +831,7 @@ usage: (defconst SYMBOL INITVALUE [DOCSTRING])  */)
   Lisp_Object sym, tem;
 
   sym = XCAR (args);
+  CHECK_SYMBOL (sym);
   Lisp_Object docstring = Qnil;
   if (!NILP (XCDR (XCDR (args))))
     {