diff --git a/lighthouse-core/lib/proto-preprocessor.js b/lighthouse-core/lib/proto-preprocessor.js
index 6e9f85331e4e..a23d1d660877 100644
--- a/lighthouse-core/lib/proto-preprocessor.js
+++ b/lighthouse-core/lib/proto-preprocessor.js
@@ -22,13 +22,23 @@ function processForProto(result) {
   /** @type {LH.Result} */
   const reportJson = JSON.parse(result);
 
+  // Clean up the configSettings
+  if (reportJson.configSettings) {
+    // make sure the 'output' field is an array
+    if (reportJson.configSettings.output) {
+      if (!Array.isArray(reportJson.configSettings.output)) {
+        reportJson.configSettings.output = [reportJson.configSettings.output];
+      }
+    }
+  }
+
   // Clean up actions that require 'audits' to exist
-  if ('audits' in reportJson) {
+  if (reportJson.audits) {
     Object.keys(reportJson.audits).forEach(auditName => {
       const audit = reportJson.audits[auditName];
 
       // Rewrite the 'not-applicable' scoreDisplayMode to 'not_applicable'. #6201
-      if ('scoreDisplayMode' in audit) {
+      if (audit.scoreDisplayMode) {
         if (audit.scoreDisplayMode === 'not-applicable') {
           // @ts-ignore Breaking the LH.Result type
           audit.scoreDisplayMode = 'not_applicable';
@@ -52,7 +62,7 @@ function processForProto(result) {
   }
 
   // Drop the i18n icuMessagePaths. Painful in proto, and low priority to expose currently.
-  if ('i18n' in reportJson && 'icuMessagePaths' in reportJson.i18n) {
+  if (reportJson.i18n && reportJson.i18n.icuMessagePaths) {
     delete reportJson.i18n.icuMessagePaths;
   }
 
diff --git a/lighthouse-core/test/lib/proto-preprocessor-test.js b/lighthouse-core/test/lib/proto-preprocessor-test.js
index 3b2b33c130df..b35982970117 100644
--- a/lighthouse-core/test/lib/proto-preprocessor-test.js
+++ b/lighthouse-core/test/lib/proto-preprocessor-test.js
@@ -9,6 +9,24 @@ const processForProto = require('../../lib/proto-preprocessor').processForProto;
 
 /* eslint-env jest */
 describe('processing for proto', () => {
+  it('cleans up configSettings', () => {
+    const input = {
+      'configSettings': {
+        'output': 'json',
+      },
+    };
+    const expectation = {
+      'configSettings': {
+        'output': [
+          'json',
+        ],
+      },
+    };
+    const output = processForProto(JSON.stringify(input));
+
+    expect(JSON.parse(output)).toMatchObject(expectation);
+  });
+
   it('cleans up audits', () => {
     const input = {
       'audits': {