diff --git a/front_end/panels/elements/ClassesPaneWidget.ts b/front_end/panels/elements/ClassesPaneWidget.ts
index 70d4519..5d99576 100644
--- a/front_end/panels/elements/ClassesPaneWidget.ts
+++ b/front_end/panels/elements/ClassesPaneWidget.ts
@@ -313,7 +313,7 @@
       if (stylesheet.frameId !== this.selectedFrameId) {
         continue;
       }
-      const cssPromise = cssModel.classNamesPromise(stylesheet.id).then(classes => {
+      const cssPromise = cssModel.getClassNames(stylesheet.id).then(classes => {
         for (const className of classes) {
           completions.add(className);
         }