diff --git a/tubular/scripts/frontend_utils.py b/tubular/scripts/frontend_utils.py
index b5182212..b6225ba7 100755
--- a/tubular/scripts/frontend_utils.py
+++ b/tubular/scripts/frontend_utils.py
@@ -122,11 +122,11 @@ def get_npm_aliases_config(self):
 
     def get_npm_private_config(self):
         """ Combines the common and environment configs NPM_PRIVATE packages """
-        npm_private_config = self.common_cfg.get('NPM_PRIVATE', {})
-        npm_private_config.update(self.env_cfg.get('NPM_PRIVATE', {}))
+        npm_private_config = self.common_cfg.get('NPM_PRIVATE', [])
+        npm_private_config.extend(self.env_cfg.get('NPM_PRIVATE', []))
         if not npm_private_config:
             self.LOG('No npm private packages defined in config.')
-        return npm_private_config
+        return list(set(npm_private_config))
 
     def build_app(self, env_vars, fail_msg):
         """ Builds the app with environment variable."""