Index: trunk/src/org/openstreetmap/josm/actions/mapmode/ParallelWayAction.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/mapmode/ParallelWayAction.java	(revision 19225)
+++ trunk/src/org/openstreetmap/josm/actions/mapmode/ParallelWayAction.java	(revision 19227)
@@ -13,4 +13,5 @@
 import java.awt.event.KeyEvent;
 import java.awt.event.MouseEvent;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -18,4 +19,5 @@
 import java.util.EnumSet;
 import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -287,5 +289,7 @@
         // Since the created way is left selected, we need to unselect again here
         if (pWays != null && pWays.getWays() != null) {
-            getLayerManager().getEditDataSet().clearSelection(pWays.getWays());
+            final List<Way> ways = new ArrayList<>(pWays.getWays());
+            ways.removeIf(w -> w.getDataSet() == null);
+            getLayerManager().getEditDataSet().clearSelection(ways);
             pWays = null;
         }