diff --git a/kernel/include/kernel/Networking/TCPSocket.h b/kernel/include/kernel/Networking/TCPSocket.h
index 3f6f41aa..583e0286 100644
--- a/kernel/include/kernel/Networking/TCPSocket.h
+++ b/kernel/include/kernel/Networking/TCPSocket.h
@@ -167,6 +167,8 @@ namespace Kernel
 		State m_next_state		{ State::Closed };
 		uint8_t m_next_flags	{ 0 };
 
+		size_t m_last_sent_window_size { 0 };
+
 		Thread* m_thread { nullptr };
 
 		// TODO: actually support these
diff --git a/kernel/kernel/Networking/TCPSocket.cpp b/kernel/kernel/Networking/TCPSocket.cpp
index b85d655a..c28bef49 100644
--- a/kernel/kernel/Networking/TCPSocket.cpp
+++ b/kernel/kernel/Networking/TCPSocket.cpp
@@ -28,6 +28,7 @@ namespace Kernel
 	BAN::ErrorOr<BAN::RefPtr<TCPSocket>> TCPSocket::create(NetworkLayer& network_layer, const Info& info)
 	{
 		auto socket = TRY(BAN::RefPtr<TCPSocket>::create(network_layer, info));
+		socket->m_last_sent_window_size = s_recv_window_buffer_size;
 		socket->m_recv_window.buffer = TRY(VirtualRange::create_to_vaddr_range(
 			PageTable::kernel(),
 			KERNEL_OFFSET,
@@ -241,6 +242,16 @@ namespace Kernel
 			memmove(recv_buffer, recv_buffer + nrecv, m_recv_window.data_size);
 		}
 
+		const bool should_update_window_size =
+			(m_last_sent_window_size == 0) ||
+			(m_recv_window.data_size == 0) ||
+			(m_last_sent_window_size + PAGE_SIZE < m_recv_window.buffer->size() - m_recv_window.data_size);
+		if (m_next_flags == 0 && should_update_window_size)
+		{
+			m_next_flags = ACK;
+			m_thread_blocker.unblock();
+		}
+
 		return total_recv;
 	}
 
@@ -502,12 +513,14 @@ namespace Kernel
 		memset(&header, 0, sizeof(TCPHeader));
 		memset(header.options, TCPOption::End, m_tcp_options_bytes);
 
+		m_last_sent_window_size = m_recv_window.buffer->size() - m_recv_window.data_size;
+
 		header.src_port = bound_port();
 		header.dst_port = dst_port;
 		header.seq_number = m_send_window.current_seq + m_send_window.has_ghost_byte;
 		header.ack_number = m_recv_window.start_seq + m_recv_window.data_size + m_recv_window.has_ghost_byte;
 		header.data_offset = (sizeof(TCPHeader) + m_tcp_options_bytes) / sizeof(uint32_t);
-		header.window_size = BAN::Math::min<size_t>(0xFFFF, m_recv_window.buffer->size() >> m_recv_window.scale_shift);
+		header.window_size = BAN::Math::min<size_t>(0xFFFF, m_last_sent_window_size >> m_recv_window.scale_shift);
 		header.flags = m_next_flags;
 		if (header.flags & FIN)
 			m_send_window.has_ghost_byte = true;
@@ -730,27 +743,28 @@ namespace Kernel
 				m_send_window.current_ack = header.ack_number;
 
 			auto payload = buffer.slice(header.data_offset * sizeof(uint32_t));
-			if (payload.size() > 0)
+			if (payload.size() > 0 && m_recv_window.data_size < m_recv_window.buffer->size())
 			{
-				if (m_recv_window.data_size + payload.size() > m_recv_window.buffer->size())
-					dprintln_if(DEBUG_TCP, "Cannot fit received bytes to window, waiting for retransmission");
-				else
+				const size_t nrecv = BAN::Math::min(payload.size(), m_recv_window.buffer->size() - m_recv_window.data_size);
+
+				auto* buffer = reinterpret_cast<uint8_t*>(m_recv_window.buffer->vaddr());
+				memcpy(buffer + m_recv_window.data_size, payload.data(), nrecv);
+				m_recv_window.data_size += nrecv;
+
+				epoll_notify(EPOLLIN);
+
+				dprintln_if(DEBUG_TCP, "Received {} bytes", nrecv);
+
+				if (m_next_flags == 0)
 				{
-					auto* buffer = reinterpret_cast<uint8_t*>(m_recv_window.buffer->vaddr());
-					memcpy(buffer + m_recv_window.data_size, payload.data(), payload.size());
-					m_recv_window.data_size += payload.size();
-
-					epoll_notify(EPOLLIN);
-
-					dprintln_if(DEBUG_TCP, "Received {} bytes", payload.size());
-
-					if (m_next_flags == 0)
-					{
-						m_next_flags = ACK;
-						m_next_state = m_state;
-					}
+					m_next_flags = ACK;
+					m_next_state = m_state;
 				}
 			}
+
+			// make sure zero window is reported
+			if (m_next_flags == 0 && m_last_sent_window_size > 0 && m_recv_window.data_size == m_recv_window.buffer->size())
+				m_next_flags = ACK;
 		}
 
 		if (!hungup_before && has_hungup_impl())