diff --git a/configure.ac b/configure.ac
index 6068cee..dc6f2dc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -120,6 +120,7 @@ AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE 1
 #endif
+#include <stdlib.h>
 #include <features.h>
 void main(void) {
 #if _XOPEN_SOURCE >= 500