diff --git a/core/modules/block/src/Tests/BlockInvalidRegionTest.php b/core/modules/block/src/Tests/BlockInvalidRegionTest.php
index 583cd72..43075d1 100644
--- a/core/modules/block/src/Tests/BlockInvalidRegionTest.php
+++ b/core/modules/block/src/Tests/BlockInvalidRegionTest.php
@@ -57,7 +57,7 @@ function testBlockInInvalidRegion() {
 
     // Place disabled test block in the invalid region of the default theme.
     $block = Block::load($block->id());
-    $block->setRegion(invalid_region');
+    $block->setRegion('invalid_region');
     $block->save();
 
     // Clear the cache to check if the warning message is not triggered.