diff --git a/builtin/clone.c b/builtin/clone.c
index c68eae13bf..f60d3271ed 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -215,6 +215,10 @@ static char *guess_dir_name(const char *repo, int is_bundle, int is_bare)
 	len = end - start;
 	strip_suffix_mem(start, &len, is_bundle ? ".bundle" : ".git");
 
+	if (!len || (len == 1 && *start == '/'))
+	    die("No directory name could be guessed.\n"
+		"Please specify a directory on the command line");
+
 	if (is_bare)
 		dir = xstrfmt("%.*s.git", (int)len, start);
 	else