diff --git a/extensions/addons.c b/extensions/addons.c
index f0dc8c95..b98899b9 100644
--- a/extensions/addons.c
+++ b/extensions/addons.c
@@ -1365,7 +1365,7 @@ addons_convert_to_simple_regexp (const gchar* pattern)
     gchar c;
 
     len = strlen (pattern);
-    dest = g_malloc0 (len * 2 + 1);
+    dest = g_malloc0 (len * 2 + 2);
     dest[0] = '^';
     pos = 1;