diff --git a/tools/jenkins/grpc_interop_php/Dockerfile b/tools/jenkins/grpc_interop_php/Dockerfile
index 492d20cdb51964f08ab073baa531a55d583aef6b..078089424b68e413521a5b5824ebd6976e43a1c3 100644
--- a/tools/jenkins/grpc_interop_php/Dockerfile
+++ b/tools/jenkins/grpc_interop_php/Dockerfile
@@ -100,6 +100,10 @@ RUN /bin/bash -l -c "rvm all do gem install ronn rake"
 RUN curl -sS https://getcomposer.org/installer | php
 RUN mv composer.phar /usr/local/bin/composer
 
+# attempt to force a rebuild of the docker image after this point because
+# Protobuf-PHP codegen has been updated
+RUN echo 1
+
 # Download the patched PHP protobuf so that PHP gRPC clients can be generated
 # from proto3 schemas.
 RUN git clone https://github.com/stanley-cheung/Protobuf-PHP.git /var/local/git/protobuf-php