diff --git a/gtk/Makefile.am b/gtk/Makefile.am
index b96e3033cb..a49803305a 100644
--- a/gtk/Makefile.am
+++ b/gtk/Makefile.am
@@ -906,7 +906,7 @@ gtktypebuiltins.c: @REBUILD@ $(gtk_public_h_sources) gtktypebuiltins.c.template
 
 gtktypefuncs.c: @REBUILD@ stamp-gtktypebuiltins.h $(top_srcdir)/gtk/*.h $(top_srcdir)/gdk/*.h Makefile
 	$(AM_V_GEN) echo '#include <gtk/gtkx.h>' > xgen-gtfsrc.c && \
-	  ${CPP} $(DEFS) $(AM_CPPFLAGS) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) xgen-gtfsrc.c | \
+	  ${CPP} $(DEFS) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) xgen-gtfsrc.c | \
 	  $(GREP) -o '\bg[td]k_[a-zA-Z0-9_]*_get_type\b' | \
 	  sort | uniq | \
 	  $(SED) '{ s/^/*tp++ = /; s/$$/();/; s/^.*\(gdk_x11\|gtk_plug_\|gtk_socket_\).*$$/#ifdef GDK_WINDOWING_X11\n&\n#endif/; }' > xgen-gtf \