diff --git a/tunnels/client/protobuf/protobuf_client.c b/tunnels/client/protobuf/protobuf_client.c
index 02a4f37..8327db0 100644
--- a/tunnels/client/protobuf/protobuf_client.c
+++ b/tunnels/client/protobuf/protobuf_client.c
@@ -18,7 +18,7 @@ enum
 {
     kMaxPacketSize    = (65536 * 1),
     kMaxRecvBeforeAck = (1 << 15) - 1,
-    kMaxSendBeforeAck = (1 << 19)
+    kMaxSendBeforeAck = (1 << 21)
 };
 
 typedef struct protobuf_client_state_s
diff --git a/tunnels/server/protobuf/protobuf_server.c b/tunnels/server/protobuf/protobuf_server.c
index d0b6edf..d13cb75 100644
--- a/tunnels/server/protobuf/protobuf_server.c
+++ b/tunnels/server/protobuf/protobuf_server.c
@@ -20,7 +20,7 @@ enum
 {
     kMaxPacketSize    = (65536 * 1),
     kMaxRecvBeforeAck = (1 << 15) - 1,
-    kMaxSendBeforeAck = (1 << 19)
+    kMaxSendBeforeAck = (1 << 21)
 };
 
 typedef struct protobuf_server_state_s