diff --git a/lib/index.ts b/lib/index.ts
index f218f8d..7acf5ea 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -105,7 +105,7 @@ class PWMetrics {
       await sheets.appendResults(results.runs);
     }
 
-    this.outputData(results);
+    await this.outputData(results);
 
     if (this.flags.expectations) {
       const resultsToCompare = this.runs > 1 ? results.median.timings : results[0].timings;
@@ -226,10 +226,10 @@ class PWMetrics {
       const formattedData = JSON.stringify(data, null, 2) + os.EOL;
       // output to file.
       if (this.flags.outputPath !== 'stdout') {
-        writeToDisk(this.flags.outputPath, formattedData);
+        return writeToDisk(this.flags.outputPath, formattedData);
       // output to stdout
       } else if (formattedData) {
-        process.stdout.write(formattedData);
+        return Promise.resolve(process.stdout.write(formattedData));
       }
     }
   }
diff --git a/lib/utils/fs.ts b/lib/utils/fs.ts
index 60c9a06..acb8b06 100644
--- a/lib/utils/fs.ts
+++ b/lib/utils/fs.ts
@@ -3,6 +3,8 @@
 
 import * as path from 'path';
 import * as fs from 'fs';
+import * as promisify from 'micro-promisify';
+
 import {getMessageWithPrefix} from './messages';
 import {Logger} from './logger';
 
@@ -27,11 +29,11 @@ export function getConfigFromFile(fileName: string = 'package.json') {
 }
 
 export function writeToDisk(fileName: string, data: string) {
-  return new Promise((resolve, reject) => {
+  return new Promise(async (resolve, reject) => {
     const filePath = path.join(process.cwd(), fileName);
 
     try {
-      fs.writeFileSync(filePath, data);
+      await promisify(fs.writeFile)(filePath, data);
     } catch (err) {
       reject(err);
     }