diff --git a/Instance/rules.make b/Instance/rules.make
index 4e3335e1..c9027cef 100644
--- a/Instance/rules.make
+++ b/Instance/rules.make
@@ -199,6 +199,14 @@ ADDITIONAL_LIBRARY_LIBS += $($(GNUSTEP_INSTANCE)_LIBS) \
 
 ADDITIONAL_LIB_DIRS += $($(GNUSTEP_INSTANCE)_LIB_DIRS)
 
+ADDITIONAL_CPPFLAGS += $($(GNUSTEP_INSTANCE)_CPPFLAGS)
+
+ADDITIONAL_CFLAGS += $($(GNUSTEP_INSTANCE)_CFLAGS)
+
+ADDITIONAL_OBJCFLAGS += $($(GNUSTEP_INSTANCE)_OBJCFLAGS)
+
+ADDITIONAL_CCFLAGS += $($(GNUSTEP_INSTANCE)_CCFLAGS)
+
 ADDITIONAL_LDFLAGS += $($(GNUSTEP_INSTANCE)_LDFLAGS)
 
 ADDITIONAL_CLASSPATH += $($(GNUSTEP_INSTANCE)_CLASSPATH)