diff -Naur a/src/Makefile.am b/src/Makefile.am
--- a/src/Makefile.am	2010-09-16 06:09:17.000000000 -0700
+++ b/src/Makefile.am	2016-09-07 22:34:28.201388863 -0700
@@ -138,7 +138,7 @@
 # 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) $(extra_cppflags) _$@ | grep GPG_ERR_ | \
+	$(CPP) $(extra_cppflags) -P _$@ | grep GPG_ERR_ | \
                $(AWK) -f $(srcdir)/mkerrcodes.awk >$@
 	-rm _$@
 
diff -Naur a/src/Makefile.in b/src/Makefile.in
--- a/src/Makefile.in	2010-10-26 02:20:52.000000000 -0700
+++ b/src/Makefile.in	2016-09-07 22:34:28.201388863 -0700
@@ -848,7 +848,7 @@
 # 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) $(extra_cppflags) _$@ | grep GPG_ERR_ | \
+	$(CPP) $(extra_cppflags) -P _$@ | grep GPG_ERR_ | \
                $(AWK) -f $(srcdir)/mkerrcodes.awk >$@
 	-rm _$@