1 files changed, 2 insertions, 1 deletions
diff --git a/lib.c b/lib.c
index e71b87cd..29049969 100644
--- a/lib.c
+++ b/lib.c
@@ -1502,7 +1502,8 @@ val cat_str(val list, val sep)
         total += len_sep;
       continue;
     }
-    return nil;
+    uw_throwf(error_s, lit("cat_str: ~s is not a character or string"),
+              item, nao);
   }
 
   str = (wchar_t *) chk_malloc((total + 1) * sizeof *str);