diff --git a/mailnews/local/tests/makefile.win b/mailnews/local/tests/makefile.win
index 416714a7301..d0a4852b793 100644
--- a/mailnews/local/tests/makefile.win
+++ b/mailnews/local/tests/makefile.win
@@ -17,6 +17,6 @@
 
 DEPTH=..\..\..
 
-DIRS=pop3
+DIRS=pop3 mailbox
 
 include <$(DEPTH)\config\rules.mak>