--- asn1/asn1c/Makefile.am.orig	2021-11-25 17:34:42 UTC
+++ asn1/asn1c/Makefile.am
@@ -70,7 +70,7 @@ libasn1c_la_SOURCES =		\
 
 EXTRA_DIST = ipa.asn1
 
-AM_CPPFLAGS = -I$(top_srcdir)/util
+AM_CPPFLAGS = -I$(top_srcdir)/util -D_GNU_SOURCE
 
 noinst_LTLIBRARIES=libasn1c.la