diff --git a/modules/purchase_trade/__init__.py b/modules/purchase_trade/__init__.py
index 171353f..30a7040 100755
--- a/modules/purchase_trade/__init__.py
+++ b/modules/purchase_trade/__init__.py
@@ -172,6 +172,7 @@ def register():
         purchase.Assay,
         purchase.AssayLine,
         purchase.AssayElement,
+        purchase.AssayUnit,
         backtoback.Backtoback,
         dimension.AnalyticDimension,
         dimension.AnalyticDimensionValue,