diff --git a/wp-includes/class-wp-image-editor-gd.php b/wp-includes/class-wp-image-editor-gd.php
index 5aa85b0eb5..acb3dd5026 100644
--- a/wp-includes/class-wp-image-editor-gd.php
+++ b/wp-includes/class-wp-image-editor-gd.php
@@ -72,7 +72,7 @@ class WP_Image_Editor_GD extends WP_Image_Editor {
 			case 'image/webp':
 				return ( $image_types & IMG_WEBP ) !== 0;
 			case 'image/avif':
-				return ( $image_types & IMG_AVIF ) !== 0;
+				return ( $image_types & IMG_AVIF ) !== 0 && function_exists( 'imageavif' );
 		}
 
 		return false;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 8a23c25205..1d98d7613e 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-58304';
+$wp_version = '6.6-alpha-58305';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.