diff --git a/docs/third_party.md b/docs/third_party.md
index 49db21b7a2..a2bb0342be 100644
--- a/docs/third_party.md
+++ b/docs/third_party.md
@@ -170,3 +170,4 @@ There are miscellaneous other things you may find useful as a Protocol Buffers d
 * [Make protoc plugins in NodeJS](https://github.com/konsumer/node-protoc-plugin)
 * [ProfaneDB - A Protocol Buffers database](https://profanedb.gitlab.io)
 * [Protocol Buffer property-based testing utility and example message generator (Python / Hypothesis)](https://github.com/CurataEng/hypothesis-protobuf)
+* [Protolock - CLI utility to prevent backward-incompatible changes to .proto files](https://github.com/nilslice/protolock)