1--- a/aclocal.in
2+++ b/aclocal.in
3@@ -314,6 +314,12 @@ sub scan_m4_dirs ($@)
4 
5   foreach my $m4dir (@dirlist)
6     {
7+      if (! -d $m4dir)
8+      {
9+        msg ('override', "warning: skipping not existing directory `$m4dir'");
10+        next;
11+      }
12+
13       if (! opendir (DIR, $m4dir))
14 	{
15 	  fatal "couldn't open directory `$m4dir': $!";
16