diff --git a/ext/phar/phar.c b/ext/phar/phar.c
index 4d5988eaa9..812720a011 100644
--- a/ext/phar/phar.c
+++ b/ext/phar/phar.c
@@ -2026,7 +2026,7 @@ next_extension:
 	}
 
 	while (pos != filename && (*(pos - 1) == '/' || *(pos - 1) == '\0')) {
-		pos = memchr(pos + 1, '.', filename_len - (pos - filename) + 1);
+		pos = memchr(pos + 1, '.', filename_len - (pos - filename) - 1);
 		if (!pos) {
 			return FAILURE;
 		}

