diff --git a/Makefile.rules b/Makefile.rules
index e3a1009..2cdb63e 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -210,9 +210,9 @@
 
 ifdef ENABLE_PROFILING
   BuildMode := Profile
-  CXX.Flags := $(OPTIMIZE_OPTION) -pg -g
-  C.Flags   := $(OPTIMIZE_OPTION) -pg -g
-  LD.Flags  := $(OPTIMIZE_OPTION) -pg -g
+  CXX.Flags += $(OPTIMIZE_OPTION) -pg -g
+  C.Flags   += $(OPTIMIZE_OPTION) -pg -g
+  LD.Flags  += $(OPTIMIZE_OPTION) -pg -g
   KEEP_SYMBOLS := 1
 else
   ifeq ($(ENABLE_OPTIMIZED),1)
@@ -229,14 +229,14 @@
       EXTRA_OPTIONS += -fstrict-aliasing
     endif
 
-    CXX.Flags := $(OPTIMIZE_OPTION) $(OmitFramePointer)
-    C.Flags   := $(OPTIMIZE_OPTION) $(OmitFramePointer)
-    LD.Flags  := $(OPTIMIZE_OPTION)
+    CXX.Flags += $(OPTIMIZE_OPTION) $(OmitFramePointer)
+    C.Flags   += $(OPTIMIZE_OPTION) $(OmitFramePointer)
+    LD.Flags  += $(OPTIMIZE_OPTION)
   else
     BuildMode := Debug
-    CXX.Flags := -g
-    C.Flags   := -g
-    LD.Flags  := -g
+    CXX.Flags += -g
+    C.Flags   += -g
+    LD.Flags  += -g
     KEEP_SYMBOLS := 1
   endif
 endif
diff --git a/bindings/ocaml/Makefile.ocaml b/bindings/ocaml/Makefile.ocaml
index 15edb01..6fc9a9a 100644
--- a/bindings/ocaml/Makefile.ocaml
+++ b/bindings/ocaml/Makefile.ocaml
@@ -20,7 +20,8 @@
 include $(LEVEL)/Makefile.config
 
 # CFLAGS needs to be set before Makefile.rules is included.
-CFLAGS += -I"$(shell $(OCAMLC) -where)"
+CXX.Flags += -I"$(shell $(OCAMLC) -where)"
+C.Flags += -I"$(shell $(OCAMLC) -where)"
 
 include $(LEVEL)/Makefile.common