diff --git a/swh/lister/gitlab/lister.py b/swh/lister/gitlab/lister.py
--- a/swh/lister/gitlab/lister.py
+++ b/swh/lister/gitlab/lister.py
@@ -161,7 +161,7 @@
         }
         if id_after is not None:
             parameters["id_after"] = str(id_after)
-        return f"{self.url}projects?{urlencode(parameters)}"
+        return f"{self.url.rstrip('/')}/projects?{urlencode(parameters)}"
 
     def get_pages(self) -> Iterator[PageResult]:
         next_page: Optional[str]