diff --git a/wp-admin/themes.php b/wp-admin/themes.php
index 465626d2d9b5..cbcde87cad97 100644
--- a/wp-admin/themes.php
+++ b/wp-admin/themes.php
@@ -20,7 +20,7 @@
 		$theme = wp_get_theme( $_GET['stylesheet'] );
 		if ( ! $theme->exists() || ! $theme->is_allowed() )
 			wp_die( __( 'Cheatin’ uh?' ) );
-		switch_theme($_GET['template'], $_GET['stylesheet']);
+		switch_theme( $theme->get_template(), $theme->get_stylesheet() );
 		wp_redirect( admin_url('themes.php?activated=true') );
 		exit;
 	} elseif ( 'delete' == $_GET['action'] ) {