diff --git a/configure.ac b/configure.ac
index d47ef5a9..3711d3bd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -12,7 +12,8 @@ AC_CONFIG_SRCDIR([free.c])
 AC_CONFIG_HEADERS([config.h])
 
 # Checks for programs.
-AC_USE_SYSTEM_EXTENSIONS(_GNU_SOURCE)
+AC_USE_SYSTEM_EXTENSIONS
+AC_SYS_LARGEFILE
 AC_PROG_AWK
 AC_PROG_CC
 AC_PROG_CC_STDC