diff --git a/src/mes.c b/src/mes.c
index 625d432a..3d489be3 100644
--- a/src/mes.c
+++ b/src/mes.c
@@ -590,6 +590,7 @@ error (SCM key, SCM x)
   eputs (": ");
   write_error_ (x);
   eputs ("\n");
+  assert (0);
   exit (1);
 }