diff --git a/make/common-defs.mk b/make/common-defs.mk
index 88b1ce806..d7383e703 100644
--- a/make/common-defs.mk
+++ b/make/common-defs.mk
@@ -155,13 +155,13 @@ endif
 CDEFS += $(BOARD_CDEFS)
 
 ifeq ($(DEBUG), YES)
-    CFLAGS += -DDEBUG
+    CPPFLAGS += -DDEBUG
 else
     CFLAGS += -fdata-sections -ffunction-sections
 endif
 
 ifeq ($(USE_CXX), YES)
-    CFLAGS += -DPIOS_ENABLE_CXX
+    CPPFLAGS += -DPIOS_ENABLE_CXX
 endif
 
 
@@ -172,8 +172,12 @@ CFLAGS += -MD -MP -MF $(OUTDIR)/dep/$(@F).d
 #CONLYFLAGS += -Wnested-externs
 CONLYFLAGS += $(CSTANDARD) -Wunsuffixed-float-constants
 
-# CPP Flags
-CPPFLAGS += -fno-rtti -fno-exceptions -std=c++11 -fno-use-cxa-atexit
+# C++ Flags
+# Note C++ compilation also uses CFLAGS.  CONLYFLAGS has exclusions that 
+# can not be used with C++ compiler. C++ specific compile options are
+# as set in CXXFLAGS. Note CPPFLAGS is for C pre-process and has not been
+# used correctly - longer term move CDEFS to CPPFLAGS.
+CXXFLAGS += -fno-rtti -fno-exceptions -std=c++11 -fno-use-cxa-atexit
 
 # Assembler flags.
 #  -Wa,...:    tell GCC to pass this to the assembler.
diff --git a/make/firmware-defs.mk b/make/firmware-defs.mk
index a464b02e9..5058f68ca 100644
--- a/make/firmware-defs.mk
+++ b/make/firmware-defs.mk
@@ -168,14 +168,14 @@ endef
 define COMPILE_C_TEMPLATE
 $(OUTDIR)/$(notdir $(basename $(1))).o : $(1)
 	@$(ECHO) $(MSG_COMPILING) $$(call toprel, $$<)
-	$(V1) $(CC) -c $(THUMB) $$(CFLAGS) $$(CONLYFLAGS) $$< -o $$@
+	$(V1) $(CC) -c $(THUMB) $$(CFLAGS) $$(CONLYFLAGS) $$(CPPFLAGS) $$< -o $$@
 endef
 
 # Compile: create object files from C source files. ARM-only
 define COMPILE_C_ARM_TEMPLATE
 $(OUTDIR)/$(notdir $(basename $(1))).o : $(1)
 	@$(ECHO) $(MSG_COMPILING_ARM) $$(call toprel, $$<)
-	$(V1) $(CC) -c $$(CFLAGS) $$(CONLYFLAGS) $$< -o $$@
+	$(V1) $(CC) -c $$(CFLAGS) $$(CONLYFLAGS) $$(CPPFLAGS) $$< -o $$@
 endef
 
 # Compile: create object files from C++ source files.
@@ -225,7 +225,7 @@ define LINK_TEMPLATE
 .PRECIOUS : $(2) $(3)
 $(1):  $(2) $(3)
 	@$(ECHO) $(MSG_LINKING) $$(call toprel, $$@)
-	$(V1) $(CC) $(THUMB) $$(CFLAGS) $(2) $(3) --output $$@ $$(LDFLAGS)
+	$(V1) $(CC) $(THUMB) $$(CFLAGS) $$(CPPFLAGS) $(2) $(3) --output $$@ $$(LDFLAGS)
 endef
 
 # Link: create ELF output file from object files.