diff --git a/src/net/net_win32/net_win32.c b/src/net/net_win32/net_win32.c
index 8e596b36..ca4d4626 100644
--- a/src/net/net_win32/net_win32.c
+++ b/src/net/net_win32/net_win32.c
@@ -140,18 +140,26 @@ NET_W32_Peer *NET_W32_TouchPeerFromKey(NET_W32_Pipe *pipe, NET_Key key)
   return peer;
 }
 
-u32 NET_W32_ChecksumFromString(String str)
+u32 NET_W32_ChecksumFromPacketString(String str)
 {
-  // Adler-32
-  // https://en.wikipedia.org/wiki/Adler-32
-  u32 a = 1;
-  u32 b = 0;
-  for (u64 idx = 0; idx < str.len; ++idx)
+  u32 result = 0;
+  if (str.len > 4)
   {
-    a = (a + str.text[idx]) % 65521;
-    b = (b + a) % 65521;
+    // Skip the first 4 bytes of packet since it contains the checksum itself
+    str.text += 4;
+    str.len -= 4;
+
+    // https://en.wikipedia.org/wiki/Adler-32
+    u32 a = 1;
+    u32 b = 0;
+    for (u64 idx = 0; idx < str.len; ++idx)
+    {
+      a = (a + str.text[idx]) % 65521;
+      b = (b + a) % 65521;
+    }
+    result = (b << 16) | a;
   }
-  return (b << 16) | a;
+  return result ^ NET_W32_ProtocolMagic;
 }
 
 ////////////////////////////////////////////////////////////
@@ -326,7 +334,6 @@ void NET_W32_TickForever(WaveLaneCtx *lane)
   for (;;)
   {
     TempArena scratch = BeginScratchNoConflict();
-    u32 magic = 0xde8c590b;
     i64 heartbeat_threshold_ns = NsFromSeconds(0.250);
     i64 passive_run_threshold_ns = NsFromSeconds(0.250);
 
@@ -596,8 +603,7 @@ void NET_W32_TickForever(WaveLaneCtx *lane)
           {
             NET_W32_PacketHeader header = Zi;
             CopyBytes(&header, buff, sizeof(header));
-            CopyBytes(buff, &magic, sizeof(magic));
-            u32 checksum = NET_W32_ChecksumFromString(STRING(len, buff));
+            u32 checksum = NET_W32_ChecksumFromPacketString(STRING(len, buff));
             if (header.checksum == checksum)
             {
               NET_Key key = NET_W32_KeyFromAddress(addr);
@@ -914,7 +920,7 @@ void NET_W32_TickForever(WaveLaneCtx *lane)
           u8 buff[Kibi(2)];
           NET_W32_PacketHeader header = Zi;
           {
-            header.checksum = magic;
+            header.checksum = 0;
             header.flags = NET_W32_PacketFlag_Heartbeat;
             header.bottom_ack = peer->bottom_ack;
             header.ack_bits = peer->ack_bits;
@@ -922,7 +928,7 @@ void NET_W32_TickForever(WaveLaneCtx *lane)
           CopyBytes(buff, &header, sizeof(header));
           buff_len += sizeof(header);
 
-          u32 checksum = NET_W32_ChecksumFromString(STRING(buff_len, buff));
+          u32 checksum = NET_W32_ChecksumFromPacketString(STRING(buff_len, buff));
           CopyBytes(buff, &checksum, sizeof(checksum));
           sendto(
             pipe->udp,
@@ -990,7 +996,7 @@ void NET_W32_TickForever(WaveLaneCtx *lane)
 
                 NET_W32_PacketHeader header = Zi;
                 {
-                  header.checksum = magic;
+                  header.checksum = 0;
                   header.flags = packet->flags;
                   header.seq = packet->seq;
                   header.msg_seq = packet->msg_seq;
@@ -1003,7 +1009,7 @@ void NET_W32_TickForever(WaveLaneCtx *lane)
                 CopyBytes(buff + buff_len, packet->data.text, packet->data.len);
                 buff_len += packet->data.len;
 
-                u32 checksum = NET_W32_ChecksumFromString(STRING(buff_len, buff));
+                u32 checksum = NET_W32_ChecksumFromPacketString(STRING(buff_len, buff));
                 CopyBytes(buff, &checksum, sizeof(checksum));
                 sendto(
                   pipe->udp,
diff --git a/src/net/net_win32/net_win32.h b/src/net/net_win32/net_win32.h
index d92de128..13940833 100644
--- a/src/net/net_win32/net_win32.h
+++ b/src/net/net_win32/net_win32.h
@@ -35,6 +35,8 @@ Struct(NET_W32_MsgBuff)
 ////////////////////////////////////////////////////////////
 //~ Packet types
 
+#define NET_W32_ProtocolMagic 0xde8c590b
+
 Enum(NET_W32_PacketFlag)
 {
   NET_W32_PacketFlag_None = 0,
@@ -180,7 +182,7 @@ NET_Key NET_W32_KeyFromAddress(struct sockaddr_in6 addr);
 struct sockaddr_in6 NET_W32_AddressFromKey(NET_Key key);
 void NET_W32_SignalWorker(void);
 NET_W32_Peer *NET_W32_TouchPeerFromKey(NET_W32_Pipe *pipe, NET_Key key);
-u32 NET_W32_ChecksumFromString(String str);
+u32 NET_W32_ChecksumFromPacketString(String str);
 
 ////////////////////////////////////////////////////////////
 //~ Worker