diff --git a/build/common.sh b/build/common.sh
index 3d052e3c93..7492dbed8f 100755
--- a/build/common.sh
+++ b/build/common.sh
@@ -154,7 +154,7 @@ function kube::build::verify_prereqs() {
   fi
   kube::build::ensure_docker_daemon_connectivity || return 1
 
-  KUBE_ROOT_HASH=$(kube::build::short_hash "$KUBE_ROOT")
+  KUBE_ROOT_HASH=$(kube::build::short_hash "${HOSTNAME:-}:${KUBE_ROOT}")
   KUBE_BUILD_IMAGE_TAG="build-${KUBE_ROOT_HASH}"
   KUBE_BUILD_IMAGE="${KUBE_BUILD_IMAGE_REPO}:${KUBE_BUILD_IMAGE_TAG}"
   KUBE_BUILD_CONTAINER_NAME="kube-build-${KUBE_ROOT_HASH}"
diff --git a/hack/update-generated-protobuf.sh b/hack/update-generated-protobuf.sh
index ff6c23feb6..2ea20b2cac 100755
--- a/hack/update-generated-protobuf.sh
+++ b/hack/update-generated-protobuf.sh
@@ -31,7 +31,7 @@ function prereqs() {
   fi
   kube::build::ensure_docker_daemon_connectivity || return 1
 
-  KUBE_ROOT_HASH=$(kube::build::short_hash "$KUBE_ROOT/go-to-protobuf")
+  KUBE_ROOT_HASH=$(kube::build::short_hash "${HOSTNAME:-}:${REPO_DIR:-${KUBE_ROOT}}/go-to-protobuf")
   KUBE_BUILD_IMAGE_TAG="build-${KUBE_ROOT_HASH}"
   KUBE_BUILD_IMAGE="${KUBE_BUILD_IMAGE_REPO}:${KUBE_BUILD_IMAGE_TAG}"
   KUBE_BUILD_CONTAINER_NAME="kube-build-${KUBE_ROOT_HASH}"