--- src/Makefile.am.orig	2015-04-04 16:29:00.437088669 +0300
+++ src/Makefile.am.orig	2015-04-04 16:29:08.468055874 +0300
@@ -204,7 +204,7 @@ 
 # 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) $(CPPFLAGS) $(extra_cppflags) _$@ | grep GPG_ERR_ | \
+	$(CPP) $(CPPFLAGS) $(extra_cppflags) -P _$@ | grep GPG_ERR_ | \
                $(AWK) -f $(srcdir)/mkerrcodes.awk >$@
 	-rm _$@
 
--- src/Makefile.in.orig	2015-04-04 16:38:31.602754217 +0300
+++ src/Makefile.in.orig	2015-04-04 16:38:41.994711716 +0300
@@ -1227,7 +1227,7 @@ 
 # 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) $(CPPFLAGS) $(extra_cppflags) _$@ | grep GPG_ERR_ | \
+	$(CPP) $(CPPFLAGS) $(extra_cppflags) -P _$@ | grep GPG_ERR_ | \
                $(AWK) -f $(srcdir)/mkerrcodes.awk >$@
 	-rm _$@