diff --git a/chromeos_version.sh b/chromeos_version.sh
index 6150bc2860..3f9d2830e9 100755
--- a/chromeos_version.sh
+++ b/chromeos_version.sh
@@ -73,7 +73,7 @@ else
   export CHROMEOS_VERSION_AUSERVER="http://$HOSTNAME:8080/update"
   export CHROMEOS_VERSION_DEVSERVER="http://$HOSTNAME:8080"
   # Overwrite CHROMEOS_VERSION_PATCH with a date string for use by auto-updater
-  export CHROMEOS_VERSION_PATCH=$(date +%Y%m%d%H%M)
+  export CHROMEOS_VERSION_PATCH=$(date +%Y_%m_%d_%H%M)
 fi
 
 # Version string. Not indentied to appease bash.