diff --git a/Server-Query-Protocol.md b/Server-Query-Protocol.md
index 4fd1647..405157e 100644
--- a/Server-Query-Protocol.md
+++ b/Server-Query-Protocol.md
@@ -29,10 +29,13 @@ where `dstring` is
 u16 length;        // including null terminator
 char data[length]; // null terminated
 ```
-The checksum function used is as follows:
+The checksum function used is a variant of CRC16:
 ```
-u32 chk = 1;
-for (u32 i = 0; i < datalen; ++i) {
-  chk = (chk + data[i]) % 65521;
+u16 x;
+u16 crc = 0xFFFF;
+for (u32 i = 0; i < buf.wp; ++i) {
+  x = crc >> 8 ^ buf.data[i];
+  x ^= x >> 4;
+  crc += (crc << 8) ^ (x << 12) ^ (x << 5) ^ x;
 }
 ```
\ No newline at end of file