diff --git a/wp-admin/themes.php b/wp-admin/themes.php
index 80d9b1983..1a49f62bd 100644
--- a/wp-admin/themes.php
+++ b/wp-admin/themes.php
@@ -120,7 +120,7 @@ $customize_title = sprintf( __( 'Customize “%s”' ), $ct->display('Na
 ?>
 <div id="current-theme" class="<?php echo esc_attr( $class ); ?>">
 	<?php if ( $screenshot ) : ?>
-		<a href="<?php echo wp_customize_url( $ct->get_stylesheet() ); ?>" class="load-customize hide-if-no-customize" title="<?php echo esc_attr( $customize_title ); ?>">
+		<a href="<?php echo wp_customize_url(); ?>" class="load-customize hide-if-no-customize" title="<?php echo esc_attr( $customize_title ); ?>">
 			<img src="<?php echo esc_url( $screenshot ); ?>" alt="<?php esc_attr_e( 'Current theme preview' ); ?>" />
 		</a>
 		<img class="hide-if-customize" src="<?php echo esc_url( $screenshot ); ?>" alt="<?php esc_attr_e( 'Current theme preview' ); ?>" />
@@ -141,7 +141,7 @@ $customize_title = sprintf( __( 'Customize &#8220;%s&#8221;' ), $ct->display('Na
 	</div>
 
 <div class="theme-options">
-	<a id="customize-current-theme-link" href="<?php echo wp_customize_url( $ct->get_stylesheet() ); ?>" class="load-customize hide-if-no-customize" title="<?php echo esc_attr( $customize_title ); ?>"><?php _e( 'Customize' )?></a>
+	<a id="customize-current-theme-link" href="<?php echo wp_customize_url(); ?>" class="load-customize hide-if-no-customize" title="<?php echo esc_attr( $customize_title ); ?>"><?php _e( 'Customize' )?></a>
 	<span><?php _e( 'Options:' )?></span>
 	<?php
 	// Pretend you didn't see this.
diff --git a/wp-includes/admin-bar.php b/wp-includes/admin-bar.php
index 6a5489cc4..b196e3ce9 100644
--- a/wp-includes/admin-bar.php
+++ b/wp-includes/admin-bar.php
@@ -580,7 +580,7 @@ function wp_admin_bar_appearance_menu( $wp_admin_bar ) {
 		'parent' => 'appearance',
 		'id'     => 'customize',
 		'title'  => __('Customize'),
-		'href'   => wp_customize_url(get_stylesheet()),
+		'href'   => wp_customize_url(),
 		'meta'   => array(
 			'class' => 'hide-if-no-customize',
 		),
diff --git a/wp-includes/theme.php b/wp-includes/theme.php
index 5485b3ed5..004a5281d 100644
--- a/wp-includes/theme.php
+++ b/wp-includes/theme.php
@@ -1615,9 +1615,14 @@ add_action( 'admin_enqueue_scripts', '_wp_customize_loader_settings' );
  * Returns a URL to load the theme customizer.
  *
  * @since 3.4.0
+ *
+ * @param string $stylesheet Optional. Theme to customize. Defaults to current theme.
  */
-function wp_customize_url( $stylesheet ) {
-	return esc_url( admin_url( 'customize.php' ) . '?theme=' . $stylesheet );
+function wp_customize_url( $stylesheet = null ) {
+	$url = admin_url( 'customize.php' );
+	if ( $stylesheet )
+		$url .= '?theme=' . $stylesheet;
+	return esc_url( $url );
 }
 
 /**