diff --git a/src/buildstream_plugins/sourcemirrors/__init__.py b/src/buildstream_plugins/sourcemirrors/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/buildstream_plugins/sourcemirrors/gitlab_lfs_mirror.py b/src/buildstream_plugins/sourcemirrors/gitlab_lfs_mirror.py
index c258cd8..a40d568 100644
--- a/src/buildstream_plugins/sourcemirrors/gitlab_lfs_mirror.py
+++ b/src/buildstream_plugins/sourcemirrors/gitlab_lfs_mirror.py
@@ -66,7 +66,7 @@ def configure(self, node):
         self.project = node.get_str("project")
         self.ref = node.get_str("ref", "master")
 
-    def translate_url(self, alias, alias_url, source_url, extra_data):
+    def translate_url(self, *, alias, alias_url, source_url, extra_data):
         project_id = quote(self.project.format(alias=alias), safe="")
         filename = quote(source_url, safe="")
 
diff --git a/src/buildstream_plugins/sourcemirrors/simple_mirror.py b/src/buildstream_plugins/sourcemirrors/simple_mirror.py
index 031e632..d22bc3c 100644
--- a/src/buildstream_plugins/sourcemirrors/simple_mirror.py
+++ b/src/buildstream_plugins/sourcemirrors/simple_mirror.py
@@ -48,7 +48,7 @@ def configure(self, node):
 
         self.url = node.get_str("url")
 
-    def translate_url(self, alias, alias_url, source_url, extra_data):
+    def translate_url(self, *, alias, alias_url, source_url, extra_data):
         base_url = self.url.format(alias=alias)
         translated_url = join(base_url, source_url)