diff --git a/configure.ac b/configure.ac
index bb7861bc0da..c7380caa196 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4727,6 +4727,8 @@ LIBS=$LIBS_no_readline
 AC_MSG_CHECKING(for broken nice())
 AC_CACHE_VAL(ac_cv_broken_nice, [
 AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <stdlib.h>
+#include <unistd.h>
 int main()
 {
 	int val1 = nice(1);