diff --git a/lib/xy.h b/lib/xy.h
index c08f66b..50915bf 100644
--- a/lib/xy.h
+++ b/lib/xy.h
@@ -289,7 +289,7 @@ xy_strdup (const char *str)
 {
   if (!str)
     {
-      fprintf (stderr, "xy.h: xy_strdup() called with NULL!");
+      fprintf (stderr, "xy.h: xy_strdup() called with NULL!\n");
       return NULL;
     }