diff --git a/src/server.h b/src/server.h
index 28a8bebf6..84735abc8 100644
--- a/src/server.h
+++ b/src/server.h
@@ -164,7 +164,7 @@ typedef long long mstime_t; /* millisecond time type. */
 #define PROTO_REPLY_CHUNK_BYTES (16*1024) /* 16k output buffer */
 #define PROTO_INLINE_MAX_SIZE   (1024*64) /* Max size of inline reads */
 #define PROTO_MBULK_BIG_ARG     (1024*32)
-#define LONG_STR_SIZE      21          /* Bytes needed for long -> str */
+#define LONG_STR_SIZE      21          /* Bytes needed for long -> str + '\0' */
 #define AOF_AUTOSYNC_BYTES (1024*1024*32) /* fdatasync every 32MB */
 
 /* When configuring the server eventloop, we setup it so that the total number