diff --git a/librarian.yaml b/librarian.yaml
index a28523a6ba41..1e2e300fc884 100644
--- a/librarian.yaml
+++ b/librarian.yaml
@@ -34,6 +34,9 @@ tools:
     - name: synthtool
       version: e643ce8e20f8fe237a31a1754524ba987de72875
       package: gcp-synthtool@git+https://github.com/googleapis/synthtool@e643ce8e20f8fe237a31a1754524ba987de72875
+  protoc:
+    version: "33.5"
+    sha256: 24e58fb231d50306ee28491f33a170301e99540f7e29ca461e0e80fd1239f8d1
 default:
   output: packages
   tag_format: '{name}-v{version}'