diff --git a/plugins/webp-uploads/hooks.php b/plugins/webp-uploads/hooks.php
index 17a2305243..ce4c38a635 100644
--- a/plugins/webp-uploads/hooks.php
+++ b/plugins/webp-uploads/hooks.php
@@ -780,3 +780,29 @@ function webp_uploads_init(): void {
 	}
 }
 add_action( 'init', 'webp_uploads_init' );
+
+/**
+ * Automatically opt into extra image sizes when generating fallback images.
+ *
+ * @since n.e.x.t
+ *
+ * @global array $_wp_additional_image_sizes Associative array of additional image sizes.
+ */
+function webp_uploads_opt_in_extra_image_sizes(): void {
+	if ( ! webp_uploads_is_fallback_enabled() ) {
+		return;
+	}
+
+	global $_wp_additional_image_sizes;
+
+	// Modify global to mimic the "hypothetical" WP core API behavior via an additional `add_image_size()` parameter.
+
+	if ( isset( $_wp_additional_image_sizes['1536x1536'] ) && ! isset( $_wp_additional_image_sizes['1536x1536']['provide_additional_mime_types'] ) ) {
+		$_wp_additional_image_sizes['1536x1536']['provide_additional_mime_types'] = true; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+	}
+
+	if ( isset( $_wp_additional_image_sizes['2048x2048'] ) && ! isset( $_wp_additional_image_sizes['2048x2048']['provide_additional_mime_types'] ) ) {
+		$_wp_additional_image_sizes['2048x2048']['provide_additional_mime_types'] = true; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+	}
+}
+add_action( 'plugins_loaded', 'webp_uploads_opt_in_extra_image_sizes' );