diff --git a/config/application.config.php b/config/application.config.php
index e7273758228dc0f9bf99e566ca564e0daae370e3..af4551da1b3c5c5f52405c0867589a4b17776cdc 100644
--- a/config/application.config.php
+++ b/config/application.config.php
@@ -3,7 +3,7 @@ $config = array(
     'modules' => array(
         'VuFindHttp', 'VuFindTheme', 'VuFind',
     ),
-    'module_listener_options' => array( 
+    'module_listener_options' => array(
         'config_glob_paths'    => array(
             'config/autoload/{,*.}{global,local}.php',
         ),
@@ -29,7 +29,7 @@ if (APPLICATION_ENV == 'development') {
 if ($localModules = getenv('VUFIND_LOCAL_MODULES')) {
     $localModules = array_map('trim', explode(',', $localModules));
     foreach ($localModules as $current) {
-        if (!empty($current)) {
+        if (!empty($current) && !in_array($current, $config['modules'])) {
             $config['modules'][] = $current;
         }
     }