diff --git a/mail/app/Makefile.in b/mail/app/Makefile.in
index e2d7c549fd5..6c59bb2c30b 100644
--- a/mail/app/Makefile.in
+++ b/mail/app/Makefile.in
@@ -193,6 +193,10 @@ endif
 
 include $(topsrcdir)/config/rules.mk
 
+ifdef MOZILLA_OFFICIAL
+DEFINES += -DMOZILLA_OFFICIAL
+endif
+
 ifdef BUILD_STATIC_LIBS
 include $(topsrcdir)/config/static-rules.mk