diff --git scripts/run-tests.sh scripts/run-tests.sh
index 503254f..332259d 100755
--- scripts/run-tests.sh
+++ scripts/run-tests.sh
@@ -113,7 +113,8 @@ All arguments are long options.
   --list      Display all available test groups.
 
   --clean     Cleans up database tables or directories from previous, failed,
-              tests and then exits (no tests are run).
+              tests and then exits (no tests are run). This also clears
+              SimpleTest's cache.
 
   --url       Immediately preceeds a URL to set the host and path. You will
               need this parameter if Drupal is in a subdirectory on your
@@ -149,8 +150,8 @@ All arguments are long options.
               specific test classes whose test methods will be run. Tests must
               be separated by commas. Ignored if --all is specified.
 
-To run this script you will normally invoke it from the root directory of your
-Drupal installation as the webserver user (differs per configuration), or root:
+To run this script you will normally invoke it as the webserver user (differs
+per configuration):
 
 sudo -u [wwwrun|www-data|etc] php ./scripts/{$args['script']}
   --url http://example.com/ --all
@@ -366,7 +367,7 @@ function simpletest_script_run_one_test($test_id, $test_class) {
 function simpletest_script_command($concurrency, $test_id, $tests) {
   global $args, $php;
 
-  $command = "$php ./scripts/{$args['script']} --url {$args['url']}";
+  $command = "$php ./scripts/{$args['script']} --url " . escapeshellarg($args['url']);
   if ($args['color']) {
     $command .= ' --color';
   }