diff --git a/locales/Makefile.in b/locales/Makefile.in
--- a/locales/Makefile.in
+++ b/locales/Makefile.in
@@ -31,19 +31,17 @@ endif
 
 DEFINES += -DAB_CD=$(AB_CD)
 
 ifneq (en-US,$(AB_CD))
 XPI_NAME               = chatzilla-$(AB_CD)
 INSTALL_EXTENSION_ID   = langpack-$(AB_CD)@chatzilla.mozilla.org
 XPI_PKGNAME            = chatzilla-$(CHATZILLA_VERSION).$(AB_CD)
 DIST_FILES             = generic/install.rdf generic/install.js
-XULAPP_DEFINES = \
-    $(DEFINES) \
-    $(ACDEFINES) \
+XULPPFLAGS += \
     -I$(call EXPAND_LOCALE_SRCDIR,toolkit/locales)/defines.inc \
     -I$(LOCALE_SRCDIR)/defines.inc \
     $(NULL)
 endif
 
 DEFINES += -DINSTALL_EXTENSION_ID="$(INSTALL_EXTENSION_ID)"
 DEFINES += -DCHATZILLA_VERSION=$(CHATZILLA_VERSION)
 DEFINES += -DCHATZILLA_BASE_VERSION=$(CHATZILLA_BASE_VERSION)