diff --git a/src/org/labkey/test/tests/SampleTypeNameExpressionTest.java b/src/org/labkey/test/tests/SampleTypeNameExpressionTest.java
index 5bff97c621..71d21e438e 100644
--- a/src/org/labkey/test/tests/SampleTypeNameExpressionTest.java
+++ b/src/org/labkey/test/tests/SampleTypeNameExpressionTest.java
@@ -67,7 +67,7 @@
 public class SampleTypeNameExpressionTest extends BaseWebDriverTest
 {
     private static final String PROJECT_NAME = "SampleType_Name_Expression_Test";
-    private static final String DEFAULT_SAMPLE_PARENT_VALUE = "SS" + TestDataGenerator.randomString(3).replaceAll("_", "."); // '_' is used as delimiter to get batchRandomId
+    private static final String DEFAULT_SAMPLE_PARENT_VALUE = "SS" + TestDataGenerator.randomString(3).replaceAll("[_)]", "."); // '_' is used as delimiter to get batchRandomId and ) is used to close the defaultValue()
 
     private static final String PARENT_SAMPLE_TYPE = "PS" + DOMAIN_TRICKY_CHARACTERS;
     private static final String PARENT_SAMPLE_TYPE_INPUT = "PS" + getEscapedNameExpression(DOMAIN_TRICKY_CHARACTERS);