--- configure.ac	2021-02-20 08:51:40.000000000 -0500
+++ configure.ac	2021-10-12 16:57:31.442711000 -0400
@@ -104,5 +104,8 @@
 	LIBS="$LIBS $lib"
 	AC_LINK_IFELSE([
-		AC_LANG_PROGRAM([#include <resolv.h>],
+		AC_LANG_PROGRAM([[#include <sys/types.h>]
+		                 [#include <netinet/in.h>]
+		                 [#include <arpa/nameser.h>]
+		                 [#include <resolv.h>]],
 		                [res_query (0, 0, 0, 0, 0)])
 	],
@@ -269,11 +272,4 @@
 else
 	AC_DEFINE_UNQUOTED(BIN_CAT, "$BIN_CAT", [path to cat, used in unit test])
-fi
-
-AC_PATH_PROG(BIN_TAC, tac, no)
-if test "$BIN_TAC" = "no" ; then
-	AC_MSG_ERROR([tac is not available])
-else
-	AC_DEFINE_UNQUOTED(BIN_TAC, "$BIN_TAC", [path to tac, used in unit test])
 fi
 
