Index: trunk/src/org/openstreetmap/josm/gui/preferences/server/OverpassServerPanel.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/preferences/server/OverpassServerPanel.java	(revision 18401)
+++ trunk/src/org/openstreetmap/josm/gui/preferences/server/OverpassServerPanel.java	(revision 18403)
@@ -16,4 +16,5 @@
 import org.openstreetmap.josm.io.OverpassDownloadReader;
 import org.openstreetmap.josm.tools.GBC;
+import org.openstreetmap.josm.tools.Utils;
 
 /**
@@ -51,5 +52,14 @@
      */
     public final void saveToPreferences() {
-        OverpassDownloadReader.OVERPASS_SERVER.put(overpassServer.getText());
+        // Get the new server -- add the trailing `/` if it does not exist to avoid duplicate entries.
+        // Other code locations assume that the URL has a trailing `/` as well.
+        String newServer = Utils.strip(overpassServer.getText());
+        if (!newServer.endsWith("/")) {
+            newServer += "/";
+        }
+        OverpassDownloadReader.OVERPASS_SERVER.put(newServer);
+        // Ensure that the new overpass server is added to history
+        overpassServer.setText(newServer);
+        overpassServer.addCurrentItemToHistory();
         overpassServer.getModel().prefs().save(OverpassDownloadReader.OVERPASS_SERVER_HISTORY);
         OverpassDownloadReader.FOR_MULTI_FETCH.put(forMultiFetch.isSelected());