diff --git a/plugins/builder-pack/builder-build b/plugins/builder-pack/builder-build
index 6c965bd2f..f26c8b930 100755
--- a/plugins/builder-pack/builder-build
+++ b/plugins/builder-pack/builder-build
@@ -15,9 +15,7 @@ trigger-builder-pack-builder-build() {
 
   local stack="$(plugn trigger buildpack-stack-name "$APP")"
   if [[ -n "$stack" ]]; then
-    DOKKU_CNB_STACK="$stack"
-  else
-    DOKKU_CNB_STACK="$DOKKU_CNB_BUILDER"
+    DOKKU_CNB_BUILDER="$stack"
   fi
 
   dokku_log_info1 "Building $APP from cnb stack $DOKKU_CNB_STACK (experimental)..."
@@ -37,7 +35,7 @@ trigger-builder-pack-builder-build() {
 
   plugn trigger pre-build-pack "$APP" "$SOURCECODE_WORK_DIR"
 
-  pack build "$IMAGE" --builder "$DOKKU_CNB_STACK" --path "$SOURCECODE_WORK_DIR" --default-process web
+  pack build "$IMAGE" --builder "$DOKKU_CNB_BUILDER" --path "$SOURCECODE_WORK_DIR" --default-process web
 
   docker-image-labeler --label=com.dokku.image-stage=build --label=com.dokku.app-name=$APP --label=org.label-schema.schema-version=1.0 --label=org.label-schema.vendor=dokku --label=dokku "$IMAGE"