diff --git a/wp-includes/rest-api.php b/wp-includes/rest-api.php
index 18a90ec2e3..83b724511a 100644
--- a/wp-includes/rest-api.php
+++ b/wp-includes/rest-api.php
@@ -1315,7 +1315,7 @@ function rest_is_boolean( $maybe_bool ) {
  * @return bool True if an integer, otherwise false.
  */
 function rest_is_integer( $maybe_integer ) {
-	return round( floatval( $maybe_integer ) ) === floatval( $maybe_integer );
+	return is_numeric( $maybe_integer ) && round( floatval( $maybe_integer ) ) === floatval( $maybe_integer );
 }
 
 /**
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 7a2fe6daca..ccde144164 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.6-alpha-48880';
+$wp_version = '5.6-alpha-48881';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.