diff --git a/lib/editor/atto/plugins/equation/db/upgrade.php b/lib/editor/atto/plugins/equation/db/upgrade.php
index 7434c24196f..c3ffde655ee 100644
--- a/lib/editor/atto/plugins/equation/db/upgrade.php
+++ b/lib/editor/atto/plugins/equation/db/upgrade.php
@@ -38,5 +38,15 @@ function xmldb_atto_equation_upgrade($oldversion) {
     // Automatically generated Moodle v4.0.0 release upgrade line.
     // Put any upgrade step following this.
 
+    if ($oldversion < 2022110700) {
+        $oldmatrix = '\left| \begin{matrix} a_1 & a_2 \\ a_3 & a_4 \end{matrix} \right|';
+        $fixedmatrix = '\left| \begin{matrix} a_1 & a_2 \\\\ a_3 & a_4 \end{matrix} \right|';
+        $config = get_config('atto_equation', 'librarygroup4');
+        $newdefault = str_replace($oldmatrix, $fixedmatrix, $config);
+        set_config('librarygroup4', $newdefault, 'atto_equation');
+        // Atto equation savepoint reached.
+        upgrade_plugin_savepoint(true, 2022110700, 'atto', 'equation');
+    }
+
     return true;
 }
diff --git a/lib/editor/atto/plugins/equation/settings.php b/lib/editor/atto/plugins/equation/settings.php
index c7e5b13fe20..118611edb6c 100644
--- a/lib/editor/atto/plugins/equation/settings.php
+++ b/lib/editor/atto/plugins/equation/settings.php
@@ -159,7 +159,7 @@ if ($ADMIN->fulltree) {
 (a)
 [a]
 \lbrace{a}\rbrace
-\left| \begin{matrix} a_1 & a_2 \\ a_3 & a_4 \end{matrix} \right|
+\left| \begin{matrix} a_1 & a_2 \\\\ a_3 & a_4 \end{matrix} \right|
 \frac{a}{b+c}
 \vec{a}
 \binom {a} {b}
diff --git a/lib/editor/atto/plugins/equation/version.php b/lib/editor/atto/plugins/equation/version.php
index a5cab505501..47e9360b6cf 100644
--- a/lib/editor/atto/plugins/equation/version.php
+++ b/lib/editor/atto/plugins/equation/version.php
@@ -24,6 +24,6 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version   = 2022041900;        // The current plugin version (Date: YYYYMMDDXX).
+$plugin->version   = 2022110700;        // The current plugin version (Date: YYYYMMDDXX).
 $plugin->requires  = 2022041200;        // Requires this Moodle version.
 $plugin->component = 'atto_equation';  // Full name of the plugin (used for diagnostics).