diff --git a/hack/update-codegen.sh b/hack/update-codegen.sh
index 11be2d3a8e69..9e0c02025d5b 100755
--- a/hack/update-codegen.sh
+++ b/hack/update-codegen.sh
@@ -18,10 +18,15 @@ set -o errexit
 set -o nounset
 set -o pipefail
 
+if [ -z "${GOPATH:-}" ]; then
+  export GOPATH=$(go env GOPATH)
+fi
+
 source $(dirname $0)/../vendor/github.com/knative/test-infra/scripts/library.sh
 
 CODEGEN_PKG=${CODEGEN_PKG:-$(cd ${REPO_ROOT_DIR}; ls -d -1 ./vendor/k8s.io/code-generator 2>/dev/null || echo ../code-generator)}
 
+
 # generate the code with:
 # --output-base    because this script should also be able to run inside the vendor dir of
 #                  k8s.io/kubernetes. The output-base is needed for the generators to output into the vendor dir
@@ -32,10 +37,12 @@ ${CODEGEN_PKG}/generate-groups.sh "deepcopy,client,informer,lister" \
   --go-header-file ${REPO_ROOT_DIR}/hack/boilerplate/boilerplate.go.txt
 
 # Depends on generate-groups.sh to install bin/deepcopy-gen
-${GOPATH}/bin/deepcopy-gen --input-dirs \
-  github.com/knative/serving/pkg/reconciler/v1alpha1/revision/config,github.com/knative/serving/pkg/autoscaler,github.com/knative/serving/pkg/logging \
+${GOPATH}/bin/deepcopy-gen \
   -O zz_generated.deepcopy \
-  --go-header-file ${REPO_ROOT_DIR}/hack/boilerplate/boilerplate.go.txt
+  --go-header-file ${REPO_ROOT_DIR}/hack/boilerplate/boilerplate.go.txt \
+  -i github.com/knative/serving/pkg/reconciler/v1alpha1/revision/config \
+  -i github.com/knative/serving/pkg/autoscaler \
+  -i github.com/knative/serving/pkg/logging
 
 # Make sure our dependencies are up-to-date
 ${REPO_ROOT_DIR}/hack/update-deps.sh