diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b24f79507ed60d4b1b5cb540b0a04d8edc9b5876..02363b9f243ccddccdeaa6812dce65de062fc629 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -38,7 +38,7 @@ testgo:
     - ls /usr/lib/go-1.15/bin
     - ls /usr/local/bin/
     - ls /usr/bin/g*
-    - /usr/lib/go-1.15/bin/go install github.com/pseudomuto/protoc-gen-doc/cmd/protoc-gen-doc@v1.4.1
+    - GO111MODULE=on /usr/lib/go-1.15/bin/go install github.com/pseudomuto/protoc-gen-doc/cmd/protoc-gen-doc@v1.4.1
 
 # Build a docker image in which tests for this repository can run
 build-testenv: