--- Makefile.in
+++ Makefile.in
@@ -22,7 +22,7 @@
 include config.make
 
 PRE_CPPFLAGS = -I.
-EXTRA_CFLAGS = $(CCPIC)
+override EXTRA_CFLAGS += $(CCPIC)
 
 # FIXME: Add configuration of LIBEXT?
 LIBTARGETS = @IF_STATIC@ libnettle.a @IF_HOGWEED@ libhogweed.a