diff --git a/tensorboard/webapp/runs/data_source/runs_data_source.ts b/tensorboard/webapp/runs/data_source/runs_data_source.ts
index 854caabc33..4870e6355e 100644
--- a/tensorboard/webapp/runs/data_source/runs_data_source.ts
+++ b/tensorboard/webapp/runs/data_source/runs_data_source.ts
@@ -74,10 +74,6 @@ function transformBackendMetricSpec(
   };
 }
 
-declare interface GetExperimentHparamRequestPayload {
-  experimentName: string;
-}
-
 @Injectable()
 export class TBRunsDataSource implements RunsDataSource {
   constructor(private readonly http: TBHttpClient) {}
@@ -98,13 +94,12 @@ export class TBRunsDataSource implements RunsDataSource {
   }
 
   fetchHparamsMetadata(experimentId: string): Observable<HparamsAndMetadata> {
-    const requestPayload: GetExperimentHparamRequestPayload = {
-      experimentName: experimentId,
-    };
+    const formData = new FormData();
+    formData.append('experimentName', experimentId);
     return this.http
       .post<backendTypes.BackendHparamsExperimentResponse>(
         `/experiment/${experimentId}/${HPARAMS_HTTP_PATH_PREFIX}/experiment`,
-        requestPayload
+        formData
       )
       .pipe(
         map((response) => {