diff --git a/c-programming/reverse-ramdisk.c b/c-programming/reverse-ramdisk.c
index 825e7f1..f36e5ea 100644
--- a/c-programming/reverse-ramdisk.c
+++ b/c-programming/reverse-ramdisk.c
@@ -67,7 +67,7 @@ int tf_alloc(size_t n, size_t type_size) {
 		line_fail(-2);
 		return -1;
 	}
-	int res = snprintf(file_path, file_path_len, "tf_%" PRIuMAX ".tmp",
+	int res = snprintf(file_path, file_path_len + 1, "tf_%" PRIuMAX ".tmp",
 		(uintmax_t) num_temp_files);
 	if ((size_t) res != file_path_len) {
 		line_fail(-2);