diff --git a/src/mol-theme/theme.ts b/src/mol-theme/theme.ts
index d654af18e25a59ea33a7fb09b4541c0d9abe9b09..940755f63c49289176c0ee66982c1de62e30d1a9 100644
--- a/src/mol-theme/theme.ts
+++ b/src/mol-theme/theme.ts
@@ -91,7 +91,7 @@ export class ThemeRegistry<T extends ColorTheme<any> | SizeTheme<any>> {
             if (a.provider.category === b.provider.category) {
                 return a.provider.label < b.provider.label ? -1 : a.provider.label > b.provider.label ? 1 : 0;
             }
-            return a.provider.category < b.provider.label ? -1 : 1;
+            return a.provider.category < b.provider.category ? -1 : 1;
         });
     }