diff --git a/cascading-core/src/main/java/cascading/tuple/TupleEntrySchemeIterator.java b/cascading-core/src/main/java/cascading/tuple/TupleEntrySchemeIterator.java
index 3149b02e59..a7f5cecad2 100644
--- a/cascading-core/src/main/java/cascading/tuple/TupleEntrySchemeIterator.java
+++ b/cascading-core/src/main/java/cascading/tuple/TupleEntrySchemeIterator.java
@@ -165,6 +165,7 @@ private TupleEntry getNext() throws IOException
     if( !hasWaiting && inputIterator.hasNext() )
       {
       sourceCall.setInput( wrapInput( inputIterator.next() ) );
+      scheme.sourcePrepare( flowProcess, sourceCall );
 
       return getNext();
       }