diff --git a/engines/base/src/main/java/org/alfresco/transform/base/transform/TransformHandler.java b/engines/base/src/main/java/org/alfresco/transform/base/transform/TransformHandler.java
index 703b208a..ad281ade 100644
--- a/engines/base/src/main/java/org/alfresco/transform/base/transform/TransformHandler.java
+++ b/engines/base/src/main/java/org/alfresco/transform/base/transform/TransformHandler.java
@@ -138,7 +138,7 @@ public class TransformHandler
             @Override
             protected long getSourceSize()
             {
-                return sourceMultipartFile.getSize();
+                return sourceMultipartFile == null ? -1 : sourceMultipartFile.getSize();
             }
 
             protected void sendTransformResponse(TransformManagerImpl transformManager)