diff --git a/src/calibre/devices/kobo/driver.py b/src/calibre/devices/kobo/driver.py
index 06e634cedb..4565d5d2af 100644
--- a/src/calibre/devices/kobo/driver.py
+++ b/src/calibre/devices/kobo/driver.py
@@ -68,7 +68,7 @@ class KOBO(USBMS):
 
     dbversion = 0
     fwversion = 0
-    supported_dbversion = 105
+    supported_dbversion = 112
     has_kepubs = False
 
     supported_platforms = ['windows', 'osx', 'linux']
@@ -1256,7 +1256,7 @@ class KOBOTOUCH(KOBO):
     description = 'Communicate with the Kobo Touch, Glo, Mini and Aura HD ereaders. Based on the existing Kobo driver by %s.' % (KOBO.author)
 #    icon        = I('devices/kobotouch.jpg')
 
-    supported_dbversion             = 105
+    supported_dbversion             = 112
     min_supported_dbversion         = 53
     min_dbversion_series            = 65
     min_dbversion_externalid        = 65
@@ -1265,7 +1265,7 @@ class KOBOTOUCH(KOBO):
     min_dbversion_activity          = 77
     min_dbversion_keywords          = 82
 
-    max_supported_fwversion         = (3, 8, 1)
+    max_supported_fwversion         = (3, 11, 1)
     min_fwversion_shelves           = (2, 0, 0)
     min_fwversion_images_on_sdcard  = (2, 4, 1)
     min_fwversion_images_tree       = (2, 9, 0)  # Cover images stored in tree under .kobo-images
@@ -1882,6 +1882,9 @@ class KOBOTOUCH(KOBO):
                 try:
                     extra_sheet = cssparseFile(extra_css_path)
                     debug_print("KoboTouch:get_extra_css: Using extra CSS in {0} ({1} rules)".format(extra_css_path, len(extra_sheet.cssRules)))
+                    if len(extra_sheet.cssRules) ==0:
+                        debug_print("KoboTouch:get_extra_css: Extra CSS file has no valid rules. CSS will not be modified.")
+                        extra_sheet = None
                 except Exception as e:
                     debug_print("KoboTouch:get_extra_css: Problem parsing extra CSS file {0}".format(extra_css_path))
                     debug_print("KoboTouch:get_extra_css: Exception {0}".format(e))
@@ -1946,6 +1949,7 @@ class KOBOTOUCH(KOBO):
 
         # Currently only modifying CSS, so if no stylesheet, don't do anything
         if not self.extra_sheet:
+            debug_print("KoboTouch:_modify_epub: no CSS file")
             return True
 
         commit_container = False