diff --git a/course/tests/course_delete_modules_test.php b/course/tests/course_delete_modules_test.php
index b1991ff44867d..6b39a8de621eb 100644
--- a/course/tests/course_delete_modules_test.php
+++ b/course/tests/course_delete_modules_test.php
@@ -101,7 +101,7 @@ public function test_delete_module_exception() {
         } catch (\coding_exception $e) {
             // Assert exception.
             $this->assertInstanceOf(\coding_exception::class, $e);
-            $errormsg = $e->getMessage();
+            $errormsg = str_replace('\\', '/', $e->getMessage()); // Normalise dir separator.
             $this->assertStringContainsString('cannotdeletemodulemissinglib', $errormsg);
             $this->assertStringContainsString('course/lib.php', $errormsg);
             $this->assertStringContainsString('mod/TestModuleToDelete/lib.php is missing', $errormsg);