diff --git a/src/org/openstreetmap/josm/data/osm/DataSetMerger.java b/src/org/openstreetmap/josm/data/osm/DataSetMerger.java
index 4306158782..93e814f6d0 100644
--- a/src/org/openstreetmap/josm/data/osm/DataSetMerger.java
+++ b/src/org/openstreetmap/josm/data/osm/DataSetMerger.java
@@ -20,6 +20,7 @@ import org.openstreetmap.josm.data.conflict.ConflictCollection;
 import org.openstreetmap.josm.gui.progress.ProgressMonitor;
 import org.openstreetmap.josm.tools.CheckParameterUtil;
 import org.openstreetmap.josm.tools.JosmRuntimeException;
+import org.openstreetmap.josm.tools.Logging;
 
 /**
  * A dataset merger which takes a target and a source dataset and merges the source data set
@@ -289,9 +290,13 @@ public class DataSetMerger {
         // found a corresponding target, remember it
         mergedMap.put(source.getPrimitiveId(), target.getPrimitiveId());
 
-        if (target.getVersion() > source.getVersion())
+        if (target.getVersion() > source.getVersion()) {
             // target.version > source.version => keep target version
+            if (Logging.isDebugEnabled()) {
+                Logging.debug("{0}/{1} has an older version: {2} < {3}", source.getType().getAPIName(), source.getOsmId(), source.getVersion(), target.getVersion());
+            }
             return true;
+        }
 
         boolean mergeFromSource = false;
         boolean haveSameVersion = target.getVersion() == source.getVersion();