diff --git a/src/org/labkey/test/util/TestDataGenerator.java b/src/org/labkey/test/util/TestDataGenerator.java
index e2e3b3383e..e7f98490de 100644
--- a/src/org/labkey/test/util/TestDataGenerator.java
+++ b/src/org/labkey/test/util/TestDataGenerator.java
@@ -68,7 +68,7 @@ public class TestDataGenerator
     private static final String ALPHANUMERIC_STRING = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvxyz";
 
     private final Map<String, PropertyDescriptor> _columns = new CaseInsensitiveLinkedHashMap<>();
-    private final Map<String, Function<List<Map<String, Object>>, Object>> _dataSuppliers = new CaseInsensitiveHashMap<>();
+    private final Map<String, Supplier<Object>> _dataSuppliers = new CaseInsensitiveHashMap<>();
     private final Set<String> _autoGeneratedFields = Collections.newSetFromMap(new CaseInsensitiveHashMap<>());
     // Rows generated for next insert or TSV dump
     private final List<Map<String, Object>> _rows = new ArrayList<>();
@@ -147,27 +147,21 @@ public TestDataGenerator withGeneratedRows(int desiredRowCount)
         return this;
     }
 
-    public TestDataGenerator addDataSupplier(String columnName, Function<List<Map<String, Object>>, Object> supplier)
-    {
-        _dataSuppliers.put(columnName, supplier);
-        return this;
-    }
-
     public TestDataGenerator addDataSupplier(String columnName, Supplier<Object> supplier)
     {
-        _dataSuppliers.put(columnName, ignored -> supplier.get());
+        _dataSuppliers.put(columnName, ()-> supplier.get());
         return this;
     }
 
     public TestDataGenerator addIntSupplier(String columnName, int min, int max)
     {
-        _dataSuppliers.put(columnName, ignored -> randomInt(min, max));
+        _dataSuppliers.put(columnName, ()-> randomInt(min, max));
         return this;
     }
 
     public TestDataGenerator addStringSupplier(String columnName, int length)
     {
-        _dataSuppliers.put(columnName, ignored -> randomString(length));
+        _dataSuppliers.put(columnName, ()-> randomString(length));
         return this;
     }
 
@@ -257,34 +251,39 @@ private Map<String, Object> generateRow()
         final Map<String, Object> newRow = new CaseInsensitiveHashMap<>();
         for (String columnName : _columns.keySet())
         {
-            if (_autoGeneratedFields.contains(columnName) || _dataSuppliers.containsKey(columnName))
+            if (!_dataSuppliers.containsKey(columnName))
+            {
+                _dataSuppliers.put(columnName, getDefaultDataSupplier(_columns.get(columnName).getRangeURI()));
+            }
+
+            if (_autoGeneratedFields.contains(columnName))
             {
                 continue;
             }
-            // Generate default values
-            Object columnValue = getDefaultDataSupplier(_columns.get(columnName).getRangeURI()).apply(_rows);
+            // Generate values
+            Object columnValue = _dataSuppliers.get(columnName).get();
             newRow.put(columnName, columnValue);
         }
         return newRow;
     }
 
-    private Function<List<Map<String, Object>>, Object> getDefaultDataSupplier(String columnType)
+    private Supplier<Object> getDefaultDataSupplier(String columnType)
     {
         switch (columnType.substring(columnType.indexOf('#') + 1).toLowerCase())
         {
             case "string":
-                return __ -> randomString(20);
+                return ()-> randomString(20);
             case "int":
-                return __ -> randomInt(0, 20);
+                return ()-> randomInt(0, 20);
             case "float":
-                return __ -> randomFloat(0, 20);
+                return ()-> randomFloat(0, 20);
             case "double":
-                return __ -> randomDouble(0, 20);
+                return ()-> randomDouble(0, 20);
             case "boolean":
-                return __ -> randomBoolean();
+                return ()-> randomBoolean();
             case "date":
             case "datetime":
-                return __ -> randomDateString(DateUtils.addWeeks(new Date(), -39), new Date());
+                return ()-> randomDateString(DateUtils.addWeeks(new Date(), -39), new Date());
             default:
                 throw new IllegalArgumentException("ColumnType " + columnType + " isn't implemented yet");
         }