--- a/aclocal.in
+++ b/aclocal.in
@@ -327,6 +327,12 @@
 
   foreach my $m4dir (@dirlist)
     {
+      if (! -d $m4dir)
+      {
+        msg ('override', "warning: skipping not existing directory `$m4dir'");
+        next;
+      }
+
       if (! opendir (DIR, $m4dir))
 	{
 	  if ($install && $type == FT_USER && $first_user_m4dir)
