diff --git a/c/src/make/compilers/gcc-target-default.cfg b/c/src/make/compilers/gcc-target-default.cfg
index fac8362661..5563475330 100644
--- a/c/src/make/compilers/gcc-target-default.cfg
+++ b/c/src/make/compilers/gcc-target-default.cfg
@@ -56,11 +56,13 @@ CFLAGS_OPTIMIZE_V+=
 CXXFLAGS_OPTIMIZE_V+=
 
 ifndef AUTOMAKE
+CPPFLAGS_$(VARIANT)=$(CPPFLAGS_$(VARIANT)_V)
 CFLAGS_$(VARIANT)  =$(CFLAGS_$(VARIANT)_V)
 CXXFLAGS_$(VARIANT)=$(CXXFLAGS_$(VARIANT)_V)
 endif
 
 ifndef AUTOMAKE
+CPPFLAGS += $(CPPFLAGS_OPTIMIZE) $(CPPFLAGS_DEBUG)
 CFLAGS   += $(CFLAGS_OPTIMIZE) $(CFLAGS_DEBUG)
 CXXFLAGS += $(CXXFLAGS_OPTIMIZE) $(CXXFLAGS_DEBUG)
 endif