diff --git a/buildbot.tac b/buildbot.tac
index f86049b..7612dcf 100644
--- a/buildbot.tac
+++ b/buildbot.tac
@@ -7,7 +7,7 @@ from buildbot.master import BuildMaster
 basedir = r'.'
 rotateLength = 10000000
 maxRotatedFiles = 10
-umask = 002
+umask = 0o02
 
 # if this is a relocatable tac file, get the directory containing the TAC
 if basedir == '.':