diff --git a/src/wp-admin/includes/class-wp-upgrader-skins.php b/src/wp-admin/includes/class-wp-upgrader-skins.php
index d196be883f..a532db201f 100644
--- a/src/wp-admin/includes/class-wp-upgrader-skins.php
+++ b/src/wp-admin/includes/class-wp-upgrader-skins.php
@@ -65,7 +65,7 @@ class WP_Upgrader_Skin {
 			$this->feedback($errors);
 		} elseif ( is_wp_error($errors) && $errors->get_error_code() ) {
 			foreach ( $errors->get_error_messages() as $message ) {
-				if ( $errors->get_error_data() )
+				if ( $errors->get_error_data() && is_string( $errors->get_error_data() ) )
 					$this->feedback($message . ' ' . esc_html( $errors->get_error_data() ) );
 				else
 					$this->feedback($message);
@@ -205,7 +205,7 @@ class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
 
 		if ( is_wp_error($error) ) {
 			foreach ( $error->get_error_messages() as $emessage ) {
-				if ( $error->get_error_data() )
+				if ( $error->get_error_data() && is_string( $error->get_error_data() ) )
 					$messages[] = $emessage . ' ' . esc_html( $error->get_error_data() );
 				else
 					$messages[] = $emessage;