diff -Naur a/src/Makefile.am b/src/Makefile.am
--- a/src/Makefile.am	2016-09-13 21:25:19.622397189 -0700
+++ b/src/Makefile.am	2016-09-13 21:28:01.216421787 -0700
@@ -138,14 +138,14 @@
 # It is correct to use $(CPP).  We want the host's idea of the error codes.
 mkerrcodes.h: Makefile mkerrcodes.awk $(gpg_extra_headers)
 	$(AWK) -f $(srcdir)/mkerrcodes1.awk $(srcdir)/errnos.in >_$@
-	$(CPP) $(extra_cppflags) -P _$@ | grep GPG_ERR_ | \
+	$(CPP) $(CPPFLAGS) $(extra_cppflags) -P _$@ | grep GPG_ERR_ | \
                $(AWK) -f $(srcdir)/mkerrcodes.awk >$@
 	-rm _$@
 
 if HAVE_W32CE_SYSTEM
 # It is correct to use $(CPP).  We want the host's idea of the error codes.
 mkw32errmap.tab.h: Makefile mkw32errmap.c
-	$(CPP) -DRESOLVE_MACROS $(srcdir)/mkw32errmap.c | \
+	$(CPP) $(CPPFLAGS) -DRESOLVE_MACROS $(srcdir)/mkw32errmap.c | \
 	      grep '{&mkw32errmap_marker' >$@
 mkw32errmap.map.c: mkw32errmap
 	./mkw32errmap --map > $@
@@ -161,7 +161,7 @@
 # the data is really to be preprocessed.
 gpg-error.def: Makefile gpg-error.def.in
 	cat $(srcdir)/gpg-error.def.in >_$@.h
-	$(CPP) $(DEFAULT_INCLUDES) $(INCLUDES) $(extra_cppflags) _$@.h | \
+	$(CPP) $(CPPFLAGS) $(DEFAULT_INCLUDES) $(INCLUDES) $(extra_cppflags) _$@.h | \
 	  grep -v '^#' >$@
 	-rm _$@.h
 
diff -Naur a/src/Makefile.in b/src/Makefile.in
--- a/src/Makefile.in	2016-09-13 21:25:19.622397189 -0700
+++ b/src/Makefile.in	2016-09-13 21:28:01.216421787 -0700
@@ -848,13 +848,13 @@
 # It is correct to use $(CPP).  We want the host's idea of the error codes.
 mkerrcodes.h: Makefile mkerrcodes.awk $(gpg_extra_headers)
 	$(AWK) -f $(srcdir)/mkerrcodes1.awk $(srcdir)/errnos.in >_$@
-	$(CPP) $(extra_cppflags) -P _$@ | grep GPG_ERR_ | \
+	$(CPP) $(CPPFLAGS) $(extra_cppflags) -P _$@ | grep GPG_ERR_ | \
                $(AWK) -f $(srcdir)/mkerrcodes.awk >$@
 	-rm _$@
 
 # It is correct to use $(CPP).  We want the host's idea of the error codes.
 @HAVE_W32CE_SYSTEM_TRUE@mkw32errmap.tab.h: Makefile mkw32errmap.c
-@HAVE_W32CE_SYSTEM_TRUE@	$(CPP) -DRESOLVE_MACROS $(srcdir)/mkw32errmap.c | \
+@HAVE_W32CE_SYSTEM_TRUE@	$(CPP) $(CPPFLAGS) -DRESOLVE_MACROS $(srcdir)/mkw32errmap.c | \
 @HAVE_W32CE_SYSTEM_TRUE@	      grep '{&mkw32errmap_marker' >$@
 @HAVE_W32CE_SYSTEM_TRUE@mkw32errmap.map.c: mkw32errmap
 @HAVE_W32CE_SYSTEM_TRUE@	./mkw32errmap --map > $@
@@ -868,7 +868,7 @@
 # the data is really to be preprocessed.
 gpg-error.def: Makefile gpg-error.def.in
 	cat $(srcdir)/gpg-error.def.in >_$@.h
-	$(CPP) $(DEFAULT_INCLUDES) $(INCLUDES) $(extra_cppflags) _$@.h | \
+	$(CPP) $(CPPFLAGS) $(DEFAULT_INCLUDES) $(INCLUDES) $(extra_cppflags) _$@.h | \
 	  grep -v '^#' >$@
 	-rm _$@.h