fix binary protocol's first byte value.
diff --git a/doc/specs/thrift-rpc.md b/doc/specs/thrift-rpc.md
index fbff3b6..a18d104 100644
--- a/doc/specs/thrift-rpc.md
+++ b/doc/specs/thrift-rpc.md
@@ -151,7 +151,7 @@
## Compatibility
A server could automatically determine whether a client talks the binary protocol or the compact protocol by
-investigating the first byte. If the value is `1000 0001` or `0000 0000` (assuming a name shorter than ±16 MB) it is the
+investigating the first byte. If the value is `1000 0000` or `0000 0000` (assuming a name shorter than ±16 MB) it is the
binary protocol. When the value is `1000 0010` it is talking the compact protocol.
## Framed vs. unframed transport