diff --git src/org/openstreetmap/gui/jmapviewer/tilesources/AbstractTMSTileSource.java src/org/openstreetmap/gui/jmapviewer/tilesources/AbstractTMSTileSource.java
index 027b550..e3dcd36 100644
--- src/org/openstreetmap/gui/jmapviewer/tilesources/AbstractTMSTileSource.java
+++ src/org/openstreetmap/gui/jmapviewer/tilesources/AbstractTMSTileSource.java
@@ -18,7 +18,7 @@ public abstract class AbstractTMSTileSource extends AbstractTileSource {
     public AbstractTMSTileSource(TileSourceInfo info) {
         this.name = info.getName();
         this.baseUrl = info.getUrl();
-        if(baseUrl.endsWith("/")) {
+        if(baseUrl != null && baseUrl.endsWith("/")) {
             baseUrl = baseUrl.substring(0,baseUrl.length()-1);
         }
         this.id = info.getUrl();