diff --git a/molecule/specs/plugins/mmc_plugin.py b/molecule/specs/plugins/mmc_plugin.py
index db8fb95..b470249 100644
--- a/molecule/specs/plugins/mmc_plugin.py
+++ b/molecule/specs/plugins/mmc_plugin.py
@@ -219,8 +219,8 @@ class ImageHandler(GenericExecutionStep, BuiltinHandlerMixin):
             env['RELEASE_DESC'] = self.metadata['release_desc']
             env['RELEASE_FILE'] = self.metadata['release_file']
             env['IMAGE_NAME'] = self.metadata['image_name']
-            env['PACKAGES_TO_ADD'] = " ".join(self.metadata.get('packages_to_add', [])
-            env['PACKAGES_TO_REMOVE'] = " ".join(self.metadata.get('packages_to_remove', [])
+            env['PACKAGES_TO_ADD'] = " ".join(self.metadata.get('packages_to_add', []))
+            env['PACKAGES_TO_REMOVE'] = " ".join(self.metadata.get('packages_to_remove', []))
             env['DESTINATION_IMAGE_DIR'] = \
                 self.metadata['destination_image_directory']