--- a/runtime/Makefile
+++ b/runtime/Makefile
@@ -335,7 +335,7 @@
 # (without the extension, which is added by the macro)
 define COMPILE_C_FILE
 $(1).$(O): %.c
-	$$(CC) -c $$(OC_CFLAGS) $$(OC_CPPFLAGS) $$(OUTPUTOBJ)$$@ $$<
+	$$(CC) -c $$(OC_CFLAGS) $(CFLAGS) $$(OC_CPPFLAGS) $$(OUTPUTOBJ)$$@ $$<
 endef
 
 object_types := % %_b %_bd %_bi %_bpic %_n %_nd %_ni %_np %_npic
--- a/yacc/Makefile
+++ b/yacc/Makefile
@@ -63,4 +63,4 @@
 # also works for .obj files.
 
 %.$(O): %.c
-	$(CC) -c $(OC_CFLAGS) $(OC_CPPFLAGS) $(OUTPUTOBJ)$@ $<
+	$(CC) -c $(OC_CFLAGS) $(CFLAGS) $(OC_CPPFLAGS) $(OUTPUTOBJ)$@ $<
--- a/otherlibs/Makefile.otherlibs.common
+++ b/otherlibs/Makefile.otherlibs.common
@@ -138,4 +138,4 @@
 	$(CAMLOPT) -c $(COMPFLAGS) $(OPTCOMPFLAGS) $<
 
 .c.$(O):
-	$(CC) -c $(OC_CFLAGS) $(OC_CPPFLAGS) $(OUTPUTOBJ)$@ $<
+	$(CC) -c $(OC_CFLAGS) $(CFLAGS) $(OC_CPPFLAGS) $(OUTPUTOBJ)$@ $<
--- a/ocamltest/Makefile
+++ b/ocamltest/Makefile
@@ -221,7 +221,7 @@
 	$(ocamllex) -q $<
 
 %.$(O): %.c
-	$(CC) $(OC_CFLAGS) $(OC_CPPFLAGS) -c $<
+	$(CC) $(OC_CFLAGS) $(CFLAGS) $(OC_CPPFLAGS) -c $<
 
 ocamltest_config.ml: ocamltest_config.ml.in Makefile ../Makefile.config
 	sed \
--- a/otherlibs/systhreads/Makefile
+++ b/otherlibs/systhreads/Makefile
@@ -93,11 +93,11 @@
 # twice, each time with different options).
 
 st_stubs_b.$(O): st_stubs.c $(HEADER)
-	$(CC) -c $(OC_CFLAGS) $(OC_CPPFLAGS) -I$(ROOTDIR)/runtime  \
+	$(CC) -c $(OC_CFLAGS) $(CFLAGS) $(OC_CPPFLAGS) -I$(ROOTDIR)/runtime  \
 	  $(SHAREDLIB_CFLAGS) $(OUTPUTOBJ)$@ $<
 
 st_stubs_n.$(O): st_stubs.c $(HEADER)
-	$(CC) $(OC_CFLAGS) $(OC_CPPFLAGS) \
+	$(CC) $(OC_CFLAGS) $(CFLAGS) $(OC_CPPFLAGS) \
 	  -I$(ROOTDIR)/runtime $(SHAREDLIB_CFLAGS) -DNATIVE_CODE \
 	  -DTARGET_$(ARCH) -DMODEL_$(MODEL) -DSYS_$(SYSTEM) \
 	  $(OUTPUTOBJ)$@ -c $<
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -322,7 +322,7 @@
 endif
 
 objinfo_helper$(EXE): objinfo_helper.c $(ROOTDIR)/runtime/caml/s.h
-	$(CC) $(OC_CFLAGS) $(OC_CPPFLAGS) -I$(ROOTDIR)/runtime $(OUTPUTEXE)$@ \
+	$(CC) $(OC_CFLAGS) $(CFLAGS) $(OC_CPPFLAGS) -I$(ROOTDIR)/runtime $(OUTPUTEXE)$@ \
           $(DEF_SYMBOL_PREFIX) $(LIBBFD_INCLUDE) $< $(LIBBFD_LINK)
 
 OBJINFO=$(ROOTDIR)/compilerlibs/ocamlcommon.cma \