diff --git a/wp-includes/js/service-worker-navigation-routing.js b/wp-includes/js/service-worker-navigation-routing.js
index 3231a0d47..a0c7be38b 100644
--- a/wp-includes/js/service-worker-navigation-routing.js
+++ b/wp-includes/js/service-worker-navigation-routing.js
@@ -65,9 +65,9 @@ ERROR_OFFLINE_BODY_FRAGMENT_URL, STREAM_HEADER_FRAGMENT_QUERY_VAR, NAVIGATION_BL
 							headers: errorResponse.headers
 						};
 
-						let body = text.replace( /<!--WP_SERVICE_WORKER_ERROR_MESSAGE-->/, errorMessages.error );
+						let body = text.replace( /[<]!--WP_SERVICE_WORKER_ERROR_MESSAGE-->/, errorMessages.error );
 						body = body.replace(
-							/(<!--WP_SERVICE_WORKER_ERROR_TEMPLATE_BEGIN-->)((?:.|\n)+?)(<!--WP_SERVICE_WORKER_ERROR_TEMPLATE_END-->)/,
+							/([<]!--WP_SERVICE_WORKER_ERROR_TEMPLATE_BEGIN-->)((?:.|\n)+?)([<]!--WP_SERVICE_WORKER_ERROR_TEMPLATE_END-->)/,
 							( details ) => {
 								if ( ! responseBody ) {
 									return ''; // Remove the details from the document entirely.
@@ -86,8 +86,8 @@ ERROR_OFFLINE_BODY_FRAGMENT_URL, STREAM_HEADER_FRAGMENT_QUERY_VAR, NAVIGATION_BL
 								details = details.replace( '{{{iframe_srcdoc}}}', srcdoc );
 
 								// Replace the comments.
-								details = details.replace( '<!--WP_SERVICE_WORKER_ERROR_TEMPLATE_BEGIN-->', '' );
-								details = details.replace( '<!--WP_SERVICE_WORKER_ERROR_TEMPLATE_END-->', '' );
+								details = details.replace( '<' + '!--WP_SERVICE_WORKER_ERROR_TEMPLATE_BEGIN-->', '' );
+								details = details.replace( '<' + '!--WP_SERVICE_WORKER_ERROR_TEMPLATE_END-->', '' );
 								return details;
 							}
 						);
@@ -111,7 +111,7 @@ ERROR_OFFLINE_BODY_FRAGMENT_URL, STREAM_HEADER_FRAGMENT_QUERY_VAR, NAVIGATION_BL
 						headers: response.headers
 					};
 
-					const body = text.replace( /<!--WP_SERVICE_WORKER_ERROR_MESSAGE-->/, errorMessages.default );
+					const body = text.replace( /[<]!--WP_SERVICE_WORKER_ERROR_MESSAGE-->/, errorMessages.default );
 
 					return new Response( body, init );
 				} );
diff --git a/wp-includes/js/service-worker-offline-commenting.js b/wp-includes/js/service-worker-offline-commenting.js
index 59bea598e..20575b293 100644
--- a/wp-includes/js/service-worker-offline-commenting.js
+++ b/wp-includes/js/service-worker-offline-commenting.js
@@ -29,9 +29,9 @@
 								headers: errorResponse.headers
 							};
 
-							let body = text.replace( /<!--WP_SERVICE_WORKER_ERROR_MESSAGE-->/, errorMessages.error );
+							let body = text.replace( /[<]!--WP_SERVICE_WORKER_ERROR_MESSAGE-->/, errorMessages.error );
 							body = body.replace(
-								/(<!--WP_SERVICE_WORKER_ERROR_TEMPLATE_BEGIN-->)((?:.|\n)+?)(<!--WP_SERVICE_WORKER_ERROR_TEMPLATE_END-->)/,
+								/([<]!--WP_SERVICE_WORKER_ERROR_TEMPLATE_BEGIN-->)((?:.|\n)+?)([<]!--WP_SERVICE_WORKER_ERROR_TEMPLATE_END-->)/,
 								( details ) => {
 									if ( ! errorText ) {
 										return ''; // Remove the details from the document entirely.
@@ -50,8 +50,8 @@
 									details = details.replace( '{{{iframe_srcdoc}}}', srcdoc );
 
 									// Replace the comments.
-									details = details.replace( '<!--WP_SERVICE_WORKER_ERROR_TEMPLATE_BEGIN-->', '' );
-									details = details.replace( '<!--WP_SERVICE_WORKER_ERROR_TEMPLATE_END-->', '' );
+									details = details.replace( '<' + '!--WP_SERVICE_WORKER_ERROR_TEMPLATE_BEGIN-->', '' );
+									details = details.replace( '<' + '!--WP_SERVICE_WORKER_ERROR_TEMPLATE_END-->', '' );
 									return details;
 								}
 							);
@@ -93,7 +93,7 @@
 							headers: response.headers
 						};
 
-						const body = text.replace( /<!--WP_SERVICE_WORKER_ERROR_MESSAGE-->/, errorMessages.comment );
+						const body = text.replace( /[<]!--WP_SERVICE_WORKER_ERROR_MESSAGE-->/, errorMessages.comment );
 
 						return new Response( body, init );
 					} );