diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index 38cd760480e..ba5ccae53ec 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -3677,9 +3677,12 @@ function xmldb_main_upgrade($oldversion) {
     }
 
     if ($oldversion < 2014062600.01) {
-        // Purge DragMath plugin which is incompatible with GNU GPL license.
-        // Hacky emulation of plugin uninstallation.
-        unset_all_config_for_plugin('tinymce_dragmath');
+        // We only want to delete DragMath if the directory no longer exists. If the directory
+        // is present then it means it has been restored, so do not perform the uninstall.
+        if (!check_dir_exists($CFG->libdir . '/editor/tinymce/plugins/dragmath', false)) {
+            // Purge DragMath plugin which is incompatible with GNU GPL license.
+            unset_all_config_for_plugin('tinymce_dragmath');
+        }
 
         // Main savepoint reached.
         upgrade_main_savepoint(true, 2014062600.01);