diff --git a/api/src/org/labkey/api/data/NameGenerator.java b/api/src/org/labkey/api/data/NameGenerator.java
index 517d7f3574e..7e45d053587 100644
--- a/api/src/org/labkey/api/data/NameGenerator.java
+++ b/api/src/org/labkey/api/data/NameGenerator.java
@@ -729,7 +729,7 @@ protected int write()
                 .filter(s -> !s.isEmpty());
     }
 
-    public static Stream<String> parentNames(Object value, String parentColName, TSVWriter tsvWriter, @Nullable BatchValidationException errors)
+    public static @Nullable Stream<String> parentNames(Object value, String parentColName, TSVWriter tsvWriter, @Nullable BatchValidationException errors)
     {
         if (value == null)
             return Stream.empty();
@@ -783,6 +783,21 @@ else if (value instanceof JSONArray jsonArray)
                 throw new IllegalStateException("For parent values in naming pattern, expected string or collection for '" + parentColName + "': " + value);
         }
 
+        if (values != null)
+        {
+            List<String> valueList = values.toList();
+            Set<String> valueSet = new HashSet<>();
+            List<String> duplicates = valueList.stream().filter(s -> !valueSet.add(s)).toList();
+            if (!duplicates.isEmpty())
+            {
+                if (errors != null)
+                    errors.addRowError(new ValidationException("Duplicate parent names found: " + StringUtils.join(duplicates, ", "), parentColName));
+                else
+                    throw new IllegalStateException("Duplicate parent names found: " + StringUtils.join(duplicates, ", "));
+            }
+            return valueList.stream();
+        }
+
         return values;
     }