diff --git a/mcrcon.c b/mcrcon.c
index f681b1c..e6b8077 100644
--- a/mcrcon.c
+++ b/mcrcon.c
@@ -568,13 +568,13 @@ rc_packet *packet_build(int id, int cmd, char *s1)
 	static rc_packet packet = {0, 0, 0, { 0x00 }};
 
 	// size + id + cmd + s1 + s2 NULL terminator
-	int s1_len = strlen(s1);
-	if (s1_len > DATA_BUFFSIZE) {
-		fprintf(stderr, "Warning: Command string too long (%d). Maximum allowed: %d.\n", s1_len, DATA_BUFFSIZE);
+	int len = strlen(s1);
+	if (len >= DATA_BUFFSIZE) {
+		fprintf(stderr, "Warning: Command string too long (%d). Maximum allowed: %d.\n", len, DATA_BUFFSIZE - 1);
 		return NULL;
 	}
 
-	packet.size = sizeof(int) * 2 + s1_len + 2;
+	packet.size = sizeof(int) * 2 + len + 2;
 	packet.id = id;
 	packet.cmd = cmd;
 	strncpy(packet.data, s1, DATA_BUFFSIZE - 1);