--- /dev/null
+--- a/aclocal.in
++++ b/aclocal.in
+@@ -295,6 +295,12 @@ sub scan_m4_dirs ($@)
+
+ foreach my $m4dir (@dirlist)
+ {
++ if (! -d $m4dir)
++ {
++ msg ('override', "warning: skipping not existing directory `$m4dir'");
++ next;
++ }
++
+ if (! opendir (DIR, $m4dir))
+ {
+ fatal "couldn't open directory `$m4dir': $!";