Index: wp-admin/includes/file.php
===================================================================
--- wp-admin/includes/file.php	(revision 47615)
+++ wp-admin/includes/file.php	(working copy)
@@ -1728,11 +1728,25 @@
 	$from = trailingslashit( $from );
 	$to   = trailingslashit( $to );
 
+    /**
+     * Filters whether to invalidate files in the PHP opcache
+     * after it is written during an upgrade.
+     *
+     * @since 5.4.0
+     *
+     * @param bool $invalidate Whether to invalidate. Default true.
+     */
+    $opcache_invalidate_allowed = function_exists( 'opcache_invalidate' ) && apply_filters('wp_opcache_invalidate_allowed', true);
+
 	foreach ( (array) $dirlist as $filename => $fileinfo ) {
 		if ( in_array( $filename, $skip_list, true ) ) {
 			continue;
 		}
 
+        if ($opcache_invalidate_allowed && in_array( pathinfo( $filename, PATHINFO_EXTENSION ), array( 'php', 'phtml' ), true ) ) {
+            opcache_invalidate( $to . $filename );
+        }
+
 		if ( 'f' === $fileinfo['type'] ) {
 			if ( ! $wp_filesystem->copy( $from . $filename, $to . $filename, true, FS_CHMOD_FILE ) ) {
 				// If copy failed, chmod file to 0644 and try again.
Index: wp-admin/includes/update-core.php
===================================================================
--- wp-admin/includes/update-core.php	(revision 47615)
+++ wp-admin/includes/update-core.php	(working copy)
@@ -1339,11 +1339,18 @@
 	$from = trailingslashit( $from );
 	$to   = trailingslashit( $to );
 
+    /** This filter is documented in wp-admin/includes/file.php */
+    $opcache_invalidate_allowed = function_exists( 'opcache_invalidate' ) && apply_filters('wp_opcache_invalidate_allowed', true);
+
 	foreach ( (array) $dirlist as $filename => $fileinfo ) {
 		if ( in_array( $filename, $skip_list, true ) ) {
 			continue;
 		}
 
+        if ($opcache_invalidate_allowed && in_array( pathinfo( $filename, PATHINFO_EXTENSION ), array( 'php', 'phtml' ), true ) ) {
+            opcache_invalidate( $to . $filename );
+        }
+
 		if ( 'f' === $fileinfo['type'] ) {
 			if ( ! $wp_filesystem->copy( $from . $filename, $to . $filename, true, FS_CHMOD_FILE ) ) {
 				// If copy failed, chmod file to 0644 and try again.