Index: /trunk/src/org/openstreetmap/josm/tools/PlatformHookWindows.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/tools/PlatformHookWindows.java	(revision 14621)
+++ /trunk/src/org/openstreetmap/josm/tools/PlatformHookWindows.java	(revision 14622)
@@ -196,8 +196,10 @@
     @Override
     public void openUrl(String url) throws IOException {
-        final String customBrowser = Config.getPref().get("browser.windows", null);
-        if (customBrowser != null) {
-            Runtime.getRuntime().exec(new String[]{customBrowser, url});
-            return;
+        if (!url.startsWith("file:/")) {
+            final String customBrowser = Config.getPref().get("browser.windows", "");
+            if (!customBrowser.isEmpty()) {
+                Runtime.getRuntime().exec(new String[]{customBrowser, url});
+                return;
+            }
         }
         try {