diff --git a/tests/kdc/krb5.conf.in b/tests/kdc/krb5.conf.in
index 8f22c4778..6c712d124 100644
--- a/tests/kdc/krb5.conf.in
+++ b/tests/kdc/krb5.conf.in
@@ -102,9 +102,14 @@
 	db-dir = @objdir@
 
 [logging]
-	kdc = 0-/FILE:@objdir@/messages.log
+	kdc = 0-/FILE=@objdir@/messages.log
 	default = 0-/FILE:@objdir@/messages.log
 
+# If you are doing preformance measurements on OSX you want to change
+# the kdc LOG line to - to = below to keep the FILE open and avoid
+# open/write/close which is blocking (rdar:// ) on OSX.
+#	kdc = 0-/FILE=@objdir@/messages.log
+
 [kadmin]
 	save-password = true
 	@dk@