diff --git a/src/add-ons/kernel/network/protocols/tcp/TCPEndpoint.cpp b/src/add-ons/kernel/network/protocols/tcp/TCPEndpoint.cpp
index 67a9bb025a..84df621a3f 100644
--- a/src/add-ons/kernel/network/protocols/tcp/TCPEndpoint.cpp
+++ b/src/add-ons/kernel/network/protocols/tcp/TCPEndpoint.cpp
@@ -666,11 +666,17 @@ TCPEndpoint::ReadData(size_t numBytes, uint32 flags, net_buffer** _buffer)
 	if (numBytes < fReceiveQueue.Available())
 		fReceiveList.Signal();
 
-	ssize_t receivedBytes = fReceiveQueue.Get(numBytes,
-		(flags & MSG_PEEK) == 0, _buffer);
+	bool clone = (flags & MSG_PEEK);
+
+	ssize_t receivedBytes = fReceiveQueue.Get(numBytes, !clone, _buffer);
 
 	TRACE("  ReadData(): %lu bytes kept.", fReceiveQueue.Available());
 
+	if (!clone) {
+		// we are opening the window, check if we should send an ACK
+		_SendQueued();
+	}
+
 	return receivedBytes;
 }