diff --git a/phpBB/adm/style/acp_ext_details.html b/phpBB/adm/style/acp_ext_details.html
index e927e9de18..f477b452b7 100644
--- a/phpBB/adm/style/acp_ext_details.html
+++ b/phpBB/adm/style/acp_ext_details.html
@@ -3,7 +3,7 @@
 <a name="maincontent"></a>
 
 	<a href="{U_BACK}" style="float: {S_CONTENT_FLOW_END};">&laquo; {L_BACK}</a>
-	
+
 	<h1>{L_EXTENSIONS_ADMIN}</h1>
 
 	<fieldset>
@@ -50,13 +50,13 @@
 	<fieldset>
 		<legend>{L_REQUIREMENTS}</legend>
 		<!-- IF MD_REQUIRE_PHPBB -->
-		<dl>
+		<dl<!-- IF MD_REQUIRE_PHPBB_FAIL --> class="requirements_not_met"<!-- ENDIF -->>
 			<dt><label for="require_phpbb">{L_PHPBB_VERSION}:</label></dt>
 			<dd><p id="require_phpbb">{MD_REQUIRE_PHPBB}</p></dd>
 		</dl>
 		<!-- ENDIF -->
 		<!-- IF MD_REQUIRE_PHP -->
-		<dl>
+		<dl<!-- IF MD_REQUIRE_PHP_FAIL --> class="requirements_not_met"<!-- ENDIF -->>
 			<dt><label for="require_php">{L_PHP_VERSION}:</label></dt>
 			<dd><p id="require_php">{MD_REQUIRE_PHP}</p></dd>
 		</dl>
diff --git a/phpBB/adm/style/admin.css b/phpBB/adm/style/admin.css
index 08613de0dd..585707600d 100644
--- a/phpBB/adm/style/admin.css
+++ b/phpBB/adm/style/admin.css
@@ -1718,3 +1718,13 @@ fieldset.permissions .padding {
 .phpinfo td, .phpinfo th, .phpinfo h2, .phpinfo h1 {
 	text-align: left;
 }
+
+.requirements_not_met {
+	padding: 5px;
+	background-color: #BC2A4D;
+}
+
+.requirements_not_met dt label, .requirements_not_met dd p {
+	color: #FFFFFF;
+	font-size: 1.4em;
+}
\ No newline at end of file
diff --git a/phpBB/includes/acp/acp_extensions.php b/phpBB/includes/acp/acp_extensions.php
index 1a9d51505a..8dde6bc36c 100644
--- a/phpBB/includes/acp/acp_extensions.php
+++ b/phpBB/includes/acp/acp_extensions.php
@@ -43,7 +43,7 @@ class acp_extensions
 
 		$action = $request->variable('action', 'list');
 		$ext_name = $request->variable('ext_name', '');
-			
+
 		// Cancel action
 		if ($request->is_set_post('cancel'))
 		{
@@ -79,9 +79,14 @@ class acp_extensions
 			break;
 
 			case 'enable_pre':
-				if (!$md_manager->validate_enable() || $phpbb_extension_manager->enabled($ext_name))
+				if (!$md_manager->validate_enable())
 				{
-					trigger_error('EXTENSION_NOT_AVAILABLE');
+					trigger_error($user->lang['EXTENSION_NOT_AVAILABLE'] . adm_back_link($this->u_action));
+				}
+
+				if ($phpbb_extension_manager->enabled($ext_name))
+				{
+					redirect($this->u_action);
 				}
 
 				$this->tpl_name = 'acp_ext_enable';
@@ -95,7 +100,7 @@ class acp_extensions
 			case 'enable':
 				if (!$md_manager->validate_enable())
 				{
-					trigger_error('EXTENSION_NOT_AVAILABLE');
+					trigger_error($user->lang['EXTENSION_NOT_AVAILABLE'] . adm_back_link($this->u_action));
 				}
 
 				if ($phpbb_extension_manager->enable_step($ext_name))
@@ -115,7 +120,7 @@ class acp_extensions
 			case 'disable_pre':
 				if (!$phpbb_extension_manager->enabled($ext_name))
 				{
-					trigger_error('EXTENSION_NOT_AVAILABLE');
+					redirect($this->u_action);
 				}
 
 				$this->tpl_name = 'acp_ext_disable';
diff --git a/phpBB/includes/extension/metadata_manager.php b/phpBB/includes/extension/metadata_manager.php
index c7f52b7c02..8a68e464a7 100644
--- a/phpBB/includes/extension/metadata_manager.php
+++ b/phpBB/includes/extension/metadata_manager.php
@@ -320,8 +320,13 @@ class phpbb_extension_metadata_manager
 			'MD_VERSION'		=> (isset($this->metadata['version'])) ? htmlspecialchars($this->metadata['version']) : '',
 			'MD_TIME'			=> (isset($this->metadata['time'])) ? htmlspecialchars($this->metadata['time']) : '',
 			'MD_LICENCE'		=> htmlspecialchars($this->metadata['licence']),
-			'MD_REQUIRE_PHP'	=> (isset($this->metadata['require']['php'])) ? htmlspecialchars($this->metadata['require']['php']) : '',
-			'MD_REQUIRE_PHPBB'	=> (isset($this->metadata['require']['phpbb'])) ? htmlspecialchars($this->metadata['require']['phpbb']) : '',
+
+			'MD_REQUIRE_PHP'		=> (isset($this->metadata['require']['php'])) ? htmlspecialchars($this->metadata['require']['php']) : '',
+			'MD_REQUIRE_PHP_FAIL'	=> !$this->validate_require_php(),
+
+			'MD_REQUIRE_PHPBB'		=> (isset($this->metadata['require']['phpbb'])) ? htmlspecialchars($this->metadata['require']['phpbb']) : '',
+			'MD_REQUIRE_PHPBB_FAIL'	=> !$this->validate_require_phpbb(),
+
 			'MD_DISPLAY_NAME'	=> (isset($this->metadata['extra']['display-name'])) ? htmlspecialchars($this->metadata['extra']['display-name']) : '',
 		));
 
diff --git a/tests/extension/acp.php b/tests/extension/acp.php
index c078a3f7b4..78a770343b 100644
--- a/tests/extension/acp.php
+++ b/tests/extension/acp.php
@@ -178,9 +178,11 @@ class acp_test extends phpbb_functional_test_case
 
 	public function test_enable_pre()
 	{
-		// Foo is already enabled (error)
+		// Foo is already enabled (redirect to list)
         $crawler = $this->request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=enable_pre&ext_name=foo&sid=' . $this->sid);
-        $this->assertContainsLang('EXTENSION_NOT_AVAILABLE', $crawler->filter('html')->text());
+        $this->assertContainsLang('EXTENSION_NAME', $crawler->filter('html')->text());
+        $this->assertContainsLang('EXTENSION_OPTIONS', $crawler->filter('html')->text());
+        $this->assertContainsLang('EXTENSION_ACTIONS', $crawler->filter('html')->text());
 
         $crawler = $this->request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=enable_pre&ext_name=vendor%2Fmoo&sid=' . $this->sid);
         $this->assertContainsLang('ENABLE_CONFIRM', $crawler->filter('html')->text());
@@ -188,9 +190,11 @@ class acp_test extends phpbb_functional_test_case
 
 	public function test_disable_pre()
 	{
-        // Moo is not enabled (error)
+        // Moo is not enabled (redirect to list)
         $crawler = $this->request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=disable_pre&ext_name=vendor%2Fmoo&sid=' . $this->sid);
-        $this->assertContainsLang('EXTENSION_NOT_AVAILABLE', $crawler->filter('html')->text());
+        $this->assertContainsLang('EXTENSION_NAME', $crawler->filter('html')->text());
+        $this->assertContainsLang('EXTENSION_OPTIONS', $crawler->filter('html')->text());
+        $this->assertContainsLang('EXTENSION_ACTIONS', $crawler->filter('html')->text());
 
         $crawler = $this->request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=disable_pre&ext_name=foo&sid=' . $this->sid);
         $this->assertContainsLang('DISABLE_CONFIRM', $crawler->filter('html')->text());
@@ -206,20 +210,14 @@ class acp_test extends phpbb_functional_test_case
         $this->assertContainsLang('PURGE_CONFIRM', $crawler->filter('html')->text());
 	}
 
-	public function test_enable()
+	public function test_actions()
 	{
         $crawler = $this->request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=enable&ext_name=vendor%2Fmoo&sid=' . $this->sid);
         $this->assertContainsLang('ENABLE_SUCCESS', $crawler->filter('html')->text());
-	}
 
-	public function test_disable()
-	{
         $crawler = $this->request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=disable&ext_name=vendor%2Fmoo&sid=' . $this->sid);
         $this->assertContainsLang('DISABLE_SUCCESS', $crawler->filter('html')->text());
-	}
 
-	public function test_purge()
-	{
         $crawler = $this->request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=purge&ext_name=vendor%2Fmoo&sid=' . $this->sid);
         $this->assertContainsLang('PURGE_SUCCESS', $crawler->filter('html')->text());
 	}