diff --git a/core/modules/text/config/install/text.settings.yml b/core/modules/text/config/install/text.settings.yml
index 1ff3cbcc9c..15697acf96 100644
--- a/core/modules/text/config/install/text.settings.yml
+++ b/core/modules/text/config/install/text.settings.yml
@@ -1 +1,2 @@
 default_summary_length: 600
+summary_marker: '<!--break-->'
\ No newline at end of file
diff --git a/core/modules/text/config/schema/text.schema.yml b/core/modules/text/config/schema/text.schema.yml
index dfc92cd2ba..1ea881843f 100644
--- a/core/modules/text/config/schema/text.schema.yml
+++ b/core/modules/text/config/schema/text.schema.yml
@@ -7,6 +7,9 @@ text.settings:
     default_summary_length:
       type: integer
       label: 'Default summary length'
+    summary_marker:
+      type: string
+      label: 'Summary marker'
 
 field.storage_settings.text:
   type: mapping
diff --git a/core/modules/text/text.install b/core/modules/text/text.install
new file mode 100644
index 0000000000..a4bed0a226
--- /dev/null
+++ b/core/modules/text/text.install
@@ -0,0 +1,13 @@
+<?php
+
+/**
+ * @file
+ * Install, update and uninstall functions for the text module.
+ */
+
+/**
+ * Update summary marker configuration setting.
+ */
+function text_update_8601() {
+  \Drupal::configFactory()->getEditable('text.settings')->set('summary_marker', '<!--break-->')->save(TRUE);
+}
diff --git a/core/modules/text/text.module b/core/modules/text/text.module
index a8c2b847fe..918a99e875 100644
--- a/core/modules/text/text.module
+++ b/core/modules/text/text.module
@@ -41,7 +41,7 @@ function text_help($route_name, RouteMatchInterface $route_match) {
 /**
  * Generates a trimmed, formatted version of a text field value.
  *
- * If the end of the summary is not indicated using the <!--break--> delimiter
+ * If the end of the summary is not indicated using the summary marker
  * then we generate the summary automatically, trying to end it at a sensible
  * place such as the end of a paragraph, a line break, or the end of a sentence
  * (in that order of preference).
@@ -55,7 +55,7 @@ function text_help($route_name, RouteMatchInterface $route_match) {
  *   from the incoming $text).
  * @param $size
  *   The desired character length of the summary. If omitted, the default value
- *   will be used. Ignored if the special delimiter is present in $text.
+ *   will be used. Ignored if a summary marker is present in $text.
  *
  * @return
  *   The generated summary.
@@ -66,17 +66,19 @@ function text_summary($text, $format = NULL, $size = NULL) {
     $size = \Drupal::config('text.settings')->get('default_summary_length');
   }
 
-  // Find where the delimiter is in the body
-  $delimiter = strpos($text, '<!--break-->');
+  // Find where the summary marker is in the body.
+  $summary_marker = \Drupal::config('text.settings')->get('summary_marker');
+  $summary_marker_position = strpos($text, $summary_marker);
 
-  // If the size is zero, and there is no delimiter, the entire body is the summary.
-  if ($size == 0 && $delimiter === FALSE) {
+  // If the size is zero, and there is no summary marker, the entire body is
+  // the summary.
+  if ($size == 0 && $summary_marker_position === FALSE) {
     return $text;
   }
 
-  // If a valid delimiter has been specified, use it to chop off the summary.
-  if ($delimiter !== FALSE) {
-    return substr($text, 0, $delimiter);
+  // If a summary marker has been found, use it to chop off the summary.
+  if ($summary_marker_position !== FALSE) {
+    return substr($text, 0, $summary_marker_position);
   }
 
   // Retrieve the filters of the specified text format, if any.
@@ -95,7 +97,7 @@ function text_summary($text, $format = NULL, $size = NULL) {
     return $text;
   }
 
-  // If the delimiter has not been specified, try to split at paragraph or
+  // If the summary marker has not been specified, try to split at paragraph or
   // sentence boundaries.
 
   // The summary may not be longer than maximum length specified. Initial slice.