diff --git a/phpBB/includes/acp/acp_extensions.php b/phpBB/includes/acp/acp_extensions.php
index 7cf15a3447..eb5fce70b5 100644
--- a/phpBB/includes/acp/acp_extensions.php
+++ b/phpBB/includes/acp/acp_extensions.php
@@ -215,10 +215,8 @@ class acp_extensions
 				}
 
 				$extension = $this->ext_manager->get_extension($ext_name);
-				if (!$extension->is_enableable())
-				{
-					trigger_error($this->user->lang['EXTENSION_NOT_ENABLEABLE'] . adm_back_link($this->u_action), E_USER_WARNING);
-				}
+
+				$this->check_is_enableable($extension);
 
 				if ($this->ext_manager->is_enabled($ext_name))
 				{
@@ -252,10 +250,8 @@ class acp_extensions
 				}
 
 				$extension = $this->ext_manager->get_extension($ext_name);
-				if (!$extension->is_enableable())
-				{
-					trigger_error($this->user->lang['EXTENSION_NOT_ENABLEABLE'] . adm_back_link($this->u_action), E_USER_WARNING);
-				}
+
+				$this->check_is_enableable($extension);
 
 				try
 				{
@@ -1130,4 +1126,28 @@ class acp_extensions
 			));
 		}
 	}
+
+	/**
+	* Checks whether the extension can be enabled. Triggers error if not.
+	* Error message can be set by the extension.
+	*
+	* @param \phpbb\extension\extension_interface $extension Extension to check
+	*/
+	protected function check_is_enableable(\phpbb\extension\extension_interface $extension)
+	{
+		$message = $extension->is_enableable();
+		if ($message !== true)
+		{
+			if (empty($message))
+			{
+				$message = $this->user->lang('EXTENSION_NOT_ENABLEABLE');
+			}
+			else if (is_array($message))
+			{
+				$message = implode('<br>', $message);
+			}
+
+			trigger_error($message . adm_back_link($this->u_action), E_USER_WARNING);
+		}
+	}
 }
diff --git a/phpBB/phpbb/console/command/extension/enable.php b/phpBB/phpbb/console/command/extension/enable.php
index a6f5b10e86..f007009aa0 100644
--- a/phpBB/phpbb/console/command/extension/enable.php
+++ b/phpBB/phpbb/console/command/extension/enable.php
@@ -69,7 +69,10 @@ class enable extends command
 		}
 		else
 		{
-			$io->error($this->user->lang('CLI_EXTENSION_ENABLE_FAILURE', $name));
+			$enableable = $this->manager->get_extension($name)->is_enableable();
+			$message = !empty($enableable) ? $enableable : $this->user->lang('CLI_EXTENSION_ENABLE_FAILURE');
+			$message = is_array($message) ? implode(PHP_EOL, $message) : $message;
+			$io->error($message, $name);
 			return 1;
 		}
 	}
diff --git a/phpBB/phpbb/extension/extension_interface.php b/phpBB/phpbb/extension/extension_interface.php
index 6a6b6adb8f..46072d420c 100644
--- a/phpBB/phpbb/extension/extension_interface.php
+++ b/phpBB/phpbb/extension/extension_interface.php
@@ -22,7 +22,8 @@ interface extension_interface
 	/**
 	* Indicate whether or not the extension can be enabled.
 	*
-	* @return bool
+	* @return bool|array	True if extension is enableable, array of reasons
+	*						if not, false for generic reason.
 	*/
 	public function is_enableable();
 
diff --git a/tests/extension/ext/vendor5/foo/composer.json b/tests/extension/ext/vendor5/foo/composer.json
new file mode 100644
index 0000000000..0fa052e188
--- /dev/null
+++ b/tests/extension/ext/vendor5/foo/composer.json
@@ -0,0 +1,23 @@
+{
+	"name": "vendor5/foo",
+	"type": "phpbb-extension",
+	"description": "An example/sample extension to be used for testing purposes in phpBB Development.",
+	"version": "1.0.0",
+	"time": "2012-02-15 01:01:01",
+	"license": "GPL-2.0",
+	"authors": [{
+			"name": "John Smith",
+			"email": "email@phpbb.com",
+			"homepage": "http://phpbb.com",
+			"role": "N/A"
+		}],
+	"require": {
+		"php": ">=5.3"
+	},
+	"extra": {
+		"display-name": "phpBB Bar Extension",
+		"soft-require": {
+			"phpbb/phpbb": "3.3.*@dev"
+		}
+	}
+}
diff --git a/tests/extension/ext/vendor5/foo/ext.php b/tests/extension/ext/vendor5/foo/ext.php
new file mode 100644
index 0000000000..6bf03f001c
--- /dev/null
+++ b/tests/extension/ext/vendor5/foo/ext.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace vendor5\foo;
+
+class ext extends \phpbb\extension\base
+{
+	static public $enabled;
+
+	public function is_enableable()
+	{
+		return array('Reason 1', 'Reason 2');
+	}
+
+	public function enable_step($old_state)
+	{
+		self::$enabled = true;
+		return self::$enabled;
+	}
+}
diff --git a/tests/extension/manager_test.php b/tests/extension/manager_test.php
index 7fac707483..128192fa0c 100644
--- a/tests/extension/manager_test.php
+++ b/tests/extension/manager_test.php
@@ -36,7 +36,7 @@ class phpbb_extension_manager_test extends phpbb_database_test_case
 	public function test_all_available()
 	{
 		// barfoo and vendor3/bar should not listed due to missing composer.json. barfoo also has incorrect dir structure.
-		$this->assertEquals(array('vendor/moo', 'vendor2/bar', 'vendor2/foo', 'vendor3/foo', 'vendor4/bar'), array_keys($this->extension_manager->all_available()));
+		$this->assertEquals(array('vendor/moo', 'vendor2/bar', 'vendor2/foo', 'vendor3/foo', 'vendor4/bar', 'vendor5/foo'), array_keys($this->extension_manager->all_available()));
 	}
 
 	public function test_all_enabled()
diff --git a/tests/functional/extension_acp_test.php b/tests/functional/extension_acp_test.php
index b398a73e3f..9a326dba68 100644
--- a/tests/functional/extension_acp_test.php
+++ b/tests/functional/extension_acp_test.php
@@ -86,7 +86,7 @@ class phpbb_functional_extension_acp_test extends phpbb_functional_test_case
 		$crawler = self::request('GET', 'adm/index.php?i=acp_extensions&mode=main&sid=' . $this->sid);
 
 		$this->assertCount(1, $crawler->filter('.ext_enabled'));
-		$this->assertCount(6, $crawler->filter('.ext_disabled'));
+		$this->assertCount(7, $crawler->filter('.ext_disabled'));
 
 		$this->assertContains('phpBB Foo Extension', $crawler->filter('.ext_enabled')->eq(0)->text());
 		$this->assertContainsLang('EXTENSION_DISABLE', $crawler->filter('.ext_enabled')->eq(0)->text());
@@ -165,9 +165,14 @@ class phpbb_functional_extension_acp_test extends phpbb_functional_test_case
 		$crawler = self::request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=enable_pre&ext_name=vendor%2Fmoo&sid=' . $this->sid);
 		$this->assertContains($this->lang('EXTENSION_ENABLE_CONFIRM', 'phpBB Moo Extension'), $crawler->filter('#main')->text());
 
-		// Correctly submit the enable form
+		// Correctly submit the enable form, default not enableable message
 		$crawler = self::request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=enable_pre&ext_name=vendor3%2Ffoo&sid=' . $this->sid);
 		$this->assertContainsLang('EXTENSION_NOT_ENABLEABLE', $crawler->filter('.errorbox')->text());
+
+		// Custom reason messages returned by not enableable extension
+		$crawler = self::request('GET', 'adm/index.php?i=acp_extensions&mode=main&action=enable_pre&ext_name=vendor5%2Ffoo&sid=' . $this->sid);
+		$this->assertContains('Reason 1', $crawler->filter('.errorbox')->text());
+		$this->assertContains('Reason 2', $crawler->filter('.errorbox')->text());
 	}
 
 	public function test_disable_pre()