diff --git a/color.c b/color.c
index 81c2676723..a9eadd190a 100644
--- a/color.c
+++ b/color.c
@@ -207,6 +207,9 @@ int color_parse_mem(const char *value, int value_len, char *dst)
 	struct color fg = { COLOR_UNSPECIFIED };
 	struct color bg = { COLOR_UNSPECIFIED };
 
+	if (!len)
+		return -1;
+
 	if (!strncasecmp(value, "reset", len)) {
 		xsnprintf(dst, end - dst, GIT_COLOR_RESET);
 		return 0;