diff --git a/phpBB/includes/acp/acp_styles.php b/phpBB/includes/acp/acp_styles.php
index d33be274b45..fde1cf48c55 100644
--- a/phpBB/includes/acp/acp_styles.php
+++ b/phpBB/includes/acp/acp_styles.php
@@ -28,6 +28,7 @@ class acp_styles
 	protected $styles_path;
 	protected $styles_path_absolute = 'styles';
 	protected $default_style = 0;
+	protected $reserved_paths = array('all', 'admin');
 
 	protected $db;
 	protected $user;
@@ -757,6 +758,13 @@ protected function find_available($all)
 				}
 			}
 
+			// Check for reserved paths
+			if (in_array($dir, $this->reserved_paths))
+			{
+				$style['_available'] = false;
+				$style['_note'] = sprintf($user->lang['RESERVED_STYLE_DIR'], htmlspecialchars($dir));
+			}
+
 			if ($all || $style['_available'])
 			{
 				$styles[] = $style;
diff --git a/phpBB/language/en/acp/styles.php b/phpBB/language/en/acp/styles.php
index f5bab1d76fc..74be6d84468 100644
--- a/phpBB/language/en/acp/styles.php
+++ b/phpBB/language/en/acp/styles.php
@@ -272,6 +272,7 @@
 	'REPLACE_THEME_EXPLAIN'		=> 'This theme will replace the one you are deleting in any styles that use it.',
 	'REPLACE_WITH_OPTION'		=> 'Replace with “%s”',
 	'REQUIRES_STYLE'			=> 'This style requires the style "%s" to be installed.',
+	'RESERVED_STYLE_DIR'		=> 'Directory "%s" is reserved, please move style to a different directory.',
 
 	'SELECT_IMAGE'				=> 'Select image',
 	'SELECT_TEMPLATE'			=> 'Select template file',