Index: src/wp-includes/compat.php
===================================================================
--- src/wp-includes/compat.php	(revision 51466)
+++ src/wp-includes/compat.php	(working copy)
@@ -371,10 +371,12 @@
 	}
 }
 
-// WebP constants are only defined in PHP 7.1+.
+// IMAGETYPE_WEBP constant is only defined in PHP 7.1 or later.
 if ( ! defined( 'IMAGETYPE_WEBP' ) ) {
 	define( 'IMAGETYPE_WEBP', 18 );
 }
+
+// IMG_WEBP constant is only defined in PHP 7.0.10 or later.
 if ( ! defined( 'IMG_WEBP' ) ) {
 	define( 'IMG_WEBP', IMAGETYPE_WEBP ); // phpcs:ignore PHPCompatibility.Constants.NewConstants.imagetype_webpFound
 }