diff --git a/gtk/Makefile.am b/gtk/Makefile.am
index 8a11903b2d..c3370e8d84 100644
--- a/gtk/Makefile.am
+++ b/gtk/Makefile.am
@@ -54,7 +54,6 @@ AM_CPPFLAGS =						\
 	-DGTK_PRINT_BACKEND_ENABLE_UNSUPPORTED		\
 	$(GTK_DEBUG_FLAGS)				\
 	$(GTK_DEP_CFLAGS)				\
-	$(gtk_clipboard_dnd_c_sources_CFLAGS)		\
 	$(INCLUDED_IMMODULE_DEFINE)
 
 if PLATFORM_WIN32
@@ -792,7 +791,8 @@ if USE_QUARTZ
 gtk_private_h_sources += 	\
 	gtksearchenginequartz.h
 gtk_c_sources += $(gtk_use_quartz_c_sources)
-gtk_use_quartz_c_sources_CFLAGS = "-xobjective-c"
+libgtk_3_la_CFLAGS = "-xobjective-c"
+
 else
 gtk_c_sources += $(gtk_use_stub_c_sources)
 endif
@@ -805,12 +805,8 @@ gtk_clipboard_dnd_c_sources = 	\
 	gtkdnd-quartz.c		\
 	gtkquartz.c
 gtk_clipboard_dnd_h_sources = gtkquartz.h
-gtk_clipboard_dnd_c_sources_CFLAGS = "-xobjective-c"
 else
-gtk_clipboard_dnd_c_sources = 	\
-	gtkclipboard.c		\
-	gtkdnd.c
-gtk_clipboard_dnd_c_sources_CFLAGS =
+gtk_clipboard_dnd_c_sources = gtkclipboard.c gtkdnd.c
 endif
 EXTRA_DIST += gtkquartz.h