diff --git a/Makefile.rules b/Makefile.rules
index 014d6973cf0..5f442d36f12 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -345,7 +345,8 @@ endif
 
 # IF REQUIRES_RTTI=1 is specified then don't disable run-time type id
 ifndef REQUIRES_RTTI
-  CXX.Flags += -fno-rtti
+  CXX.Flags := $(filter-out -fno-rtti,$(CXX.Flags))
+  CXXFLAGS := $(filter-out -fno-rtti,$(CXXFLAGS))
 endif
 
 ifdef ENABLE_COVERAGE