2 files changed, 7 insertions, 1 deletions
diff --git a/ChangeLog b/ChangeLog
index 783aa5a2..acef717f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2012-01-26  Kaz Kylheku  <kaz@kylheku.com>
 
+	* lib.c (cat_str): Throw error if one of the list elements
+	is not a character or string instead of silently returning nil.
+
+2012-01-26  Kaz Kylheku  <kaz@kylheku.com>
+
 	* txr.1: More discussion of ranges.
 
 2012-01-26  Kaz Kylheku  <kaz@kylheku.com>
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);