diff --git a/lib/commands/merge.js b/lib/commands/merge.js
index 0aefd11ec..758c6f536 100644
--- a/lib/commands/merge.js
+++ b/lib/commands/merge.js
@@ -41,6 +41,6 @@ exports.handler = cliWrapper(async argv => {
   }
   await makeDir(path.dirname(argv.outputFile))
   const map = await nyc.getCoverageMapFromAllCoverageFiles(argv.inputDirectory)
-  await fs.writeFile(argv.outputFile, JSON.stringify(map, null, 2), 'utf8')
+  await fs.writeFile(argv.outputFile, JSON.stringify(map), 'utf8')
   console.info(`coverage files in ${argv.inputDirectory} merged into ${argv.outputFile}`)
 })