diff --git a/lib/rbs/collection/sources/stdlib.rb b/lib/rbs/collection/sources/stdlib.rb
index f78a8b6bac..3ba9154410 100644
--- a/lib/rbs/collection/sources/stdlib.rb
+++ b/lib/rbs/collection/sources/stdlib.rb
@@ -17,7 +17,7 @@ def has?(name, version)
         end
 
         def versions(name)
-          REPO.gems[name].versions.keys.map(&:to_s)
+          REPO.gems[name].version_names.map(&:to_s)
         end
 
         def install(dest:, name:, version:, stdout:)
diff --git a/lib/rbs/repository.rb b/lib/rbs/repository.rb
index 49285975d9..eb9602d957 100644
--- a/lib/rbs/repository.rb
+++ b/lib/rbs/repository.rb
@@ -43,7 +43,7 @@ def load!
       end
 
       def version_names
-        versions.keys.sort_by(&:version)
+        versions.keys.sort
       end
 
       def oldest_version