diff -Naur ExtUtils-AutoInstall-0.63.orig/lib/ExtUtils/AutoInstall.pm ExtUtils-AutoInstall-0.63/lib/ExtUtils/AutoInstall.pm
--- ExtUtils-AutoInstall-0.63.orig/lib/ExtUtils/AutoInstall.pm	2005-09-12 15:16:09.000000000 +0200
+++ ExtUtils-AutoInstall-0.63/lib/ExtUtils/AutoInstall.pm	2014-04-04 18:27:58.840550357 +0200
@@ -878,9 +878,14 @@
     }
 
     $args{test}{TESTS} ||= 't/*.t';
-    $args{test}{TESTS} = join(' ', grep {
-        !exists($DisabledTests{$_})
-    } map { glob($_) } split(/\s+/, $args{test}{TESTS}));
+
+    # Only expand the list of tests if we absolutely have to to avoid
+    # blowing over command line limits.
+    if( keys %DisabledTests ) {
+	$args{test}{TESTS} = join(' ', grep {
+	    !exists($DisabledTests{$_})
+	} map { glob($_) } split(/\s+/, $args{test}{TESTS}));
+    }
 
     my $missing = join(',', @Missing);
     my $config  = join(',',