diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index 190b985..736c66b 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -258,7 +258,7 @@ function simpletest_script_parse_args() {
     'php' => '',
     'concurrency' => 1,
     'all' => FALSE,
-    'all-simpletests' => FALSE,
+    'all-simpletest' => FALSE,
     'module' => NULL,
     'class' => FALSE,
     'file' => FALSE,
@@ -800,7 +800,7 @@ function simpletest_script_get_test_list() {
     $groups = simpletest_test_get_all($args['module']);
     $all_tests = array();
     foreach ($groups as $group => $tests) {
-      if ($args['all-simpletests']) {
+      if ($args['all-simpletest']) {
         $tests = array_filter($tests, function($test_class) {
           return !is_subclass_of($test_class, '\PHPUnit_Framework_TestCase');
         });