diff --git a/gconf/gapplookupgconf.c b/gconf/gapplookupgconf.c
index 059659d..75e3b32 100644
--- a/gconf/gapplookupgconf.c
+++ b/gconf/gapplookupgconf.c
@@ -114,6 +114,9 @@ get_default_for_uri_scheme (GDesktopAppInfoLookup *lookup,
 
   appinfo = NULL;
   
+  if (uri_scheme == NULL || *uri_scheme == '\0')
+    uri_scheme = "unknown";
+
   client = gconf_client_get_default ();
   
   command_key = g_strconcat (GCONF_PATH_PREFIX,