diff --git a/overviewer.py b/overviewer.py
index 3a191b5..3ae3494 100755
--- a/overviewer.py
+++ b/overviewer.py
@@ -117,7 +117,7 @@ def main():
     parser.add_option("-v", "--verbose", dest="verbose", action="count", default=0, helptext="Print more output. You can specify this option multiple times.")
     parser.add_option("--skip-js", dest="skipjs", action="store_true", helptext="Don't output marker.js or regions.js")
     parser.add_option("--no-signs", dest="nosigns", action="store_true", helptext="Don't output signs to markers.js")
-    parser.add_option("--north-direction", dest="north_direction", helptext="Specifies which corner of the screen north will point to. Valid options are: " + ", ".join(avail_north_dirs) + ".", type="choice", default=avail_north_dirs[0], choices=avail_north_dirs)
+    parser.add_option("--north-direction", dest="north_direction", action="store", helptext="Specifies which corner of the screen north will point to. Valid options are: " + ", ".join(avail_north_dirs) + ".", type="choice", default=avail_north_dirs[0], choices=avail_north_dirs)
     parser.add_option("--display-config", dest="display_config", action="store_true", helptext="Display the configuration parameters, but don't render the map.  Requires all required options to be specified", commandLineOnly=True)
     #parser.add_option("--write-config", dest="write_config", action="store_true", helptext="Writes out a sample config file", commandLineOnly=True)
 
@@ -241,6 +241,13 @@ def main():
     
     # First do world-level preprocessing
     w = world.World(worlddir, destdir, useBiomeData=useBiomeData, regionlist=regionlist, north_direction=north_direction)
+    if not (w.persistentData['north_direction'] == north_direction) and not options.forcerender:
+        logging.error("Conflicting north-direction setting!")
+        logging.error("Overviewer.dat gives previous north-direction as "+w.persistentData['north_direction'])
+        logging.error("Requested north-direction was "+north_direction)
+        logging.error("To change north-direction of an existing render, --forcerender must be specified")
+        sys.exit(1)
+    
     w.go(options.procs)
 
     logging.info("Rending the following tilesets: %s", ",".join(options.rendermode))
diff --git a/overviewer_core/googlemap.py b/overviewer_core/googlemap.py
index 82b4869..9a4e95e 100644
--- a/overviewer_core/googlemap.py
+++ b/overviewer_core/googlemap.py
@@ -187,6 +187,7 @@ class MapGen(object):
         
         # save persistent data
         self.world.persistentData['POI'] = self.world.POI
+        self.world.persistentData['north_direction'] = self.world.north_direction
         with open(self.world.pickleFile,"wb") as f:
             cPickle.dump(self.world.persistentData,f)
 
diff --git a/overviewer_core/world.py b/overviewer_core/world.py
index 59b77c5..2f5e7f7 100644
--- a/overviewer_core/world.py
+++ b/overviewer_core/world.py
@@ -135,9 +135,11 @@ class World(object):
         if os.path.exists(self.pickleFile):
             with open(self.pickleFile,"rb") as p:
                 self.persistentData = cPickle.load(p)
+                if not self.persistentData.get('north_direction', False):
+                    self.persistentData['north_direction']=='lower-left'
         else:
             # some defaults
-            self.persistentData = dict(POI=[])
+            self.persistentData = dict(POI=[], north_direction=self.north_direction)
         
  
     def get_region_path(self, chunkX, chunkY):