diff --git a/lustre/autoconf/lustre-core.m4 b/lustre/autoconf/lustre-core.m4
index 34f43f672603d3e9ff7c65ee3ea2ed662b1efa43..a510c0006aebcc00378e7405061e8a65fe61d877 100644
--- a/lustre/autoconf/lustre-core.m4
+++ b/lustre/autoconf/lustre-core.m4
@@ -1250,12 +1250,14 @@ AC_TRY_RUN([
 
 #include <stdio.h>
 
-main(void)
+int main(void)
 {
     int size = mds_xattr_acl_size(LUSTRE_POSIX_ACL_MAX_ENTRIES);
     FILE *f = fopen("acl.size","w+");
     fprintf(f,"%d", size);
     fclose(f);
+
+    return 0;
 }
 
 ],[