diff --git a/ikcp.c b/ikcp.c
index 4d933f1..149d873 100644
--- a/ikcp.c
+++ b/ikcp.c
@@ -901,7 +901,7 @@ void ikcp_flush(ikcpcb *kcp)
 	if (kcp->probe & IKCP_ASK_SEND) {
 		seg.cmd = IKCP_CMD_WASK;
 		size = (int)(ptr - buffer);
-		if (size + IKCP_OVERHEAD >= (int)kcp->mtu) {
+		if (size + IKCP_OVERHEAD > (int)kcp->mtu) {
 			ikcp_output(kcp, buffer, size);
 			ptr = buffer;
 		}
@@ -912,7 +912,7 @@ void ikcp_flush(ikcpcb *kcp)
 	if (kcp->probe & IKCP_ASK_TELL) {
 		seg.cmd = IKCP_CMD_WINS;
 		size = (int)(ptr - buffer);
-		if (size + IKCP_OVERHEAD >= (int)kcp->mtu) {
+		if (size + IKCP_OVERHEAD > (int)kcp->mtu) {
 			ikcp_output(kcp, buffer, size);
 			ptr = buffer;
 		}