Index: trunk/src/org/openstreetmap/josm/tools/PlatformHookOsx.java
===================================================================
--- trunk/src/org/openstreetmap/josm/tools/PlatformHookOsx.java	(revision 7282)
+++ trunk/src/org/openstreetmap/josm/tools/PlatformHookOsx.java	(revision 7283)
@@ -62,4 +62,7 @@
     public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
         Boolean handled = Boolean.TRUE;
+        if (Main.isDebugEnabled()) {
+            Main.debug("OSX handler: "+method.getName()+" - "+args);
+        }
         switch (method.getName()) {
         case "openFiles":
@@ -69,8 +72,12 @@
                     if (oFiles instanceof List) {
                         OpenFileAction.openFiles((List<File>)oFiles, true);
+                    } else {
+                        Main.warn("OSX openFiles called without List: "+oFiles);
                     }
                 } catch (ReflectiveOperationException | SecurityException | IllegalArgumentException ex) {
                     Main.warn("Failed to access open files event: " + ex);
                 }
+            } else {
+                Main.warn("OSX openFiles called without args");
             }
             return null;