Index: src/ipeui/Makefile
--- src/ipeui/Makefile.orig
+++ src/ipeui/Makefile
@@ -15,6 +15,7 @@ ifdef IPE_SPELLCHECK
 CPPFLAGS += -DIPE_SPELLCHECK
 endif
 CXXFLAGS += $(UI_CFLAGS) $(LUA_CFLAGS) $(DLL_CFLAGS) $(SPELL_CFLAGS)
+CPPFLAGS += $(CXXFLAGS)
 LIBS += $(UI_LIBS) $(LUA_LIBS) $(SPELL_LIBS)
 
 all: $(TARGET)
