diff -u b/modules/simpletest/simpletest.module b/modules/simpletest/simpletest.module
--- b/modules/simpletest/simpletest.module
+++ b/modules/simpletest/simpletest.module
@@ -371,7 +371,7 @@
           // If this test class requires a non-existing module, skip it.
           if (!empty($info['dependencies'])) {
 
-            // Searching for an item that does not exist returns NULL.
+            // Searching for an item that does not exist triggers an PHP error.
             // Set a custom error handler so we can ignore the file not found error.
             set_error_handler(function($error_level, $message, $filename, $line, $context) {
               // Skip error handling if this is a "file not found" error.
@@ -383,6 +383,8 @@
 
             foreach ($info['dependencies'] as $module) {
               if (!drupal_get_filename('module', $module)) {
+                // Restore the original error handler.
+                restore_error_handler();
                 continue 2;
               }
             }
diff -u b/modules/simpletest/tests/bootstrap.test b/modules/simpletest/tests/bootstrap.test
--- b/modules/simpletest/tests/bootstrap.test
+++ b/modules/simpletest/tests/bootstrap.test
@@ -435,10 +435,10 @@
     restore_error_handler();
 
     // Get the bad records static from drupal_get_filename.
-    $bad = &drupal_static('drupal_get_filename:missing');
+    $missing = &drupal_static('drupal_get_filename:missing');
 
     // Searching for an item that does not exist creates a static record in drupal_get_filename.
-    $this->assertTrue($bad['module'][$non_existing_module], 'Searching for an item that does not exist creates a static record in drupal_get_filename.');
+    $this->assertTrue($missing['module'][$non_existing_module], 'Searching for an item that does not exist creates a static record in drupal_get_filename.');
   }
 }