diff --git a/packages/benchpress/src/metric/perflog_metric.ts b/packages/benchpress/src/metric/perflog_metric.ts
index 391a97ff90..3ef69f9061 100644
--- a/packages/benchpress/src/metric/perflog_metric.ts
+++ b/packages/benchpress/src/metric/perflog_metric.ts
@@ -156,7 +156,7 @@ export class PerflogMetric extends Metric {
         return result;
       }
       let resolve: (result: any) => void;
-      const promise = new Promise(res => { resolve = res; });
+      const promise = new Promise<{[key: string]: number}>(res => { resolve = res; });
       this._setTimeout(() => resolve(this._readUntilEndMark(markName, loopCount + 1)), 100);
       return promise;
     });
diff --git a/packages/benchpress/src/webdriver/firefox_driver_extension.ts b/packages/benchpress/src/webdriver/firefox_driver_extension.ts
index 0c3c360632..9c895259cb 100644
--- a/packages/benchpress/src/webdriver/firefox_driver_extension.ts
+++ b/packages/benchpress/src/webdriver/firefox_driver_extension.ts
@@ -40,7 +40,7 @@ export class FirefoxDriverExtension extends WebDriverExtension {
     return this._driver.executeScript(script);
   }
 
-  readPerfLog(): Promise<PerfLogEvent> {
+  readPerfLog(): Promise<PerfLogEvent[]> {
     return this._driver.executeAsyncScript('var cb = arguments[0]; window.getProfile(cb);');
   }