There is a new option "minZoomLevel" with a default value of 12.

The OfflineLayer will report an error when trying to calculate the nb of tiles or to save tiles with a map zoomed out more than that limit.

src/OfflineLayer.coffee

@@ -20,6 +20,9 @@ module.exports = class OfflineLayer extends L.TileLayer
     dbOption = options["dbOption"]
     storeName = options["storeName"] || 'OfflineLeafletTileImages'
     @_tileImagesStore = null
+    @_minZoomLevel = 12
+    if options["minZoomLevel"]?
+      @_minZoomLevel = parseInt(options["minZoomLevel"])
 
     if dbOption? and dbOption != "None"
       try
@@ -123,6 +126,10 @@ module.exports = class OfflineLayer extends L.TileLayer
 
   # calculateNbTiles includes potentially already saved tiles.
   calculateNbTiles: (zoomLevelLimit) ->
+    if @_map.getZoom() < @_minZoomLevel
+      @_reportError("ZOOM_LEVEL_TOO_LOW")
+      return -1
+
     count = 0
     tileImagesToQuery = @_getTileImages(zoomLevelLimit)
     for key of tileImagesToQuery
@@ -192,6 +199,11 @@ module.exports = class OfflineLayer extends L.TileLayer
       onError("system is busy.")
       return
 
+    if @_map.getZoom() < @_minZoomLevel
+      @_reportError("ZOOM_LEVEL_TOO_LOW")
+      onError("ZOOM_LEVEL_TOO_LOW")
+      return
+
     #lock UI
     tileImagesToQuery = @_getTileImages(zoomLevelLimit)
     @_tileImagesStore.saveImages(tileImagesToQuery, onStarted, onSuccess, (error) =>

src/demo.coffee

@@ -52,6 +52,8 @@ class CacheBtnControl extends L.Control
     # Might be a good idea to put a limit on the number of tiles that can would be saved
     # calculateNbTiles includes potentially already saved tiles.
     nbTiles = offlineLayer.calculateNbTiles();
+    if nbTiles == -1
+      return
     if(nbTiles < 10000)
       console.log("Will be saving: " + nbTiles + " tiles");