diff --git a/lib/utils/process.py b/lib/utils/process.py
index cc1c9ed06aac9ddb9aa1a892d267b0f57c7bf6bd..4eef342e042f39a0596fb16c36eced5634e83d08 100644
--- a/lib/utils/process.py
+++ b/lib/utils/process.py
@@ -110,6 +110,8 @@ class RunResult(object):
 
     if fail_msgs and self.failed:
       self.fail_reason = utils_text.CommaJoin(fail_msgs)
+    else:
+      self.fail_reason = None
 
     if self.failed:
       logging.debug("Command '%s' failed (%s); output: %s",