diff --git a/lib/utils/build-name-from-env.js b/lib/utils/build-name-from-env.js
index <HASH>..<HASH> 100644
--- a/lib/utils/build-name-from-env.js
+++ b/lib/utils/build-name-from-env.js
@@ -2,7 +2,7 @@ module.exports = function() {
   let buildNum = process.env.TRAVIS_JOB_NUMBER || process.env.BITBUCKET_BUILD_NUMBER || process.env.CIRCLE_BUILD_NUM;
   let prefix = process.env.BROWSERSTACK_BUILD_NAME_PREFIX;
   if (buildNum && prefix) {
-    return prefix + '-' + buildNum;
+    return prefix + '_' + buildNum;
   }
   return buildNum;
 }
Dashes are not allowed in build names, use underscore