Index: wp-content/themes/twentyfifteen/inc/back-compat.php
===================================================================
--- wp-content/themes/twentyfifteen/inc/back-compat.php	(revision 36560)
+++ wp-content/themes/twentyfifteen/inc/back-compat.php	(working copy)
@@ -34,8 +34,7 @@
  * @since Twenty Fifteen 1.0
  */
 function twentyfifteen_upgrade_notice() {
-	$message = sprintf( __( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ), $GLOBALS['wp_version'] );
-	printf( '<div class="error"><p>%s</p></div>', $message );
+	printf( '<div class="error"><p>%s</p></div>', twentyfifteen_minimum_required_version_message() );
 }
 
 /**
@@ -44,7 +43,7 @@
  * @since Twenty Fifteen 1.0
  */
 function twentyfifteen_customize() {
-	wp_die( sprintf( __( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ), $GLOBALS['wp_version'] ), '', array(
+	wp_die( twentyfifteen_minimum_required_version_message(), '', array(
 		'back_link' => true,
 	) );
 }
@@ -57,7 +56,21 @@
  */
 function twentyfifteen_preview() {
 	if ( isset( $_GET['preview'] ) ) {
-		wp_die( sprintf( __( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ), $GLOBALS['wp_version'] ) );
+		wp_die( twentyfifteen_minimum_required_version_message() );
 	}
 }
 add_action( 'template_redirect', 'twentyfifteen_preview' );
+
+/**
+ * Minimum required WordPress version message.
+ *
+ * @since Twenty Fifteen 1.5
+ */
+function twentyfifteen_minimum_required_version_message() {
+	$message = sprintf(
+		/* translators: %s: WordPress version */
+		__( 'Twenty Fifteen requires at least WordPress version 4.1. You are running version %s. Please upgrade and try again.', 'twentyfifteen' ),
+		$GLOBALS['wp_version']
+	);
+	return $message;
+}