diff --git a/lib/blocks.php b/lib/blocks.php
index bffc2f1645396..1d5692889b091 100644
--- a/lib/blocks.php
+++ b/lib/blocks.php
@@ -102,8 +102,8 @@ function do_blocks( $content ) {
 	global $wp_registered_blocks;
 
 	// Extract the blocks from the post content.
-	$open_matcher = '/<!--\s*wp:([a-z](?:[a-z0-9\/]+)*)\s+((?:(?!-->).)*)-->.*?<!--\s*\/wp:\g1\s+-->/';
-	preg_match_all( $open_matcher, $content, $matches, PREG_OFFSET_CAPTURE );
+	$matcher = '/<!--\s*wp:([a-z](?:[a-z0-9\/]+)*)\s+((?:(?!-->).)*)\s*\/?-->(?:.*?<!--\s*\/wp:\g1\s+-->)?/';
+	preg_match_all( $matcher, $content, $matches, PREG_OFFSET_CAPTURE );
 
 	$new_content = $content;
 	foreach ( $matches[0] as $index => $block_match ) {
@@ -114,7 +114,6 @@ function do_blocks( $content ) {
 		}
 
 		$block_markup = $block_match[0];
-		$block_position = $block_match[1];
 		$block_attributes_string = $matches[2][ $index ][0];
 		$block_attributes = parse_block_attributes( $block_attributes_string );