diff --git a/base b/base
index ab837d73b..4a91eefe3 160000
--- a/base
+++ b/base
@@ -1 +1 @@
-Subproject commit ab837d73bae87efeb92950b4f00b6b55e5d45927
+Subproject commit 4a91eefe3a42f926ebe262658c258c9929544836
diff --git a/frontend/apps/reader/modules/readerrolling.lua b/frontend/apps/reader/modules/readerrolling.lua
index 5e1d24dff..cbf15737f 100644
--- a/frontend/apps/reader/modules/readerrolling.lua
+++ b/frontend/apps/reader/modules/readerrolling.lua
@@ -258,6 +258,11 @@ function ReaderRolling:onCloseDocument()
         end
     end
     logger.dbg("cre cache used:", cache_file_path or "none")
+    -- Unknown elements and attributes, uncomment if needed for debugging:
+    -- local elements, attributes, namespaces = self.ui.document:getUnknownEntities()
+    -- if elements ~= "" then logger.info("cre unknown elements: ", elements) end
+    -- if attributes ~= "" then logger.info("cre unknown attributes: ", attributes) end
+    -- if namespaces ~= "" then logger.info("cre unknown namespaces: ", namespaces) end
 end
 
 function ReaderRolling:onCheckDomStyleCoherence()
diff --git a/frontend/document/credocument.lua b/frontend/document/credocument.lua
index 5d16baf11..4f171c245 100644
--- a/frontend/document/credocument.lua
+++ b/frontend/document/credocument.lua
@@ -205,6 +205,14 @@ function CreDocument:setupDefaultView()
         self._document:setIntProperty("crengine.page.header.font.size",
             G_reader_settings:readSetting("cre_header_status_font_size"))
     end
+
+    -- One can set these to change from white background
+    if G_reader_settings:readSetting("cre_background_color") then
+        self:setBackgroundColor(G_reader_settings:readSetting("cre_background_color"))
+    end
+    if G_reader_settings:readSetting("cre_background_image") then
+        self:setBackgroundImage(G_reader_settings:readSetting("cre_background_image"))
+    end
 end
 
 function CreDocument:loadDocument(full_document)
@@ -893,6 +901,11 @@ function CreDocument:setStatusLineProp(prop)
     self._document:setStringProperty("window.status.line", prop)
 end
 
+function CreDocument:setBackgroundColor(bgcolor) -- use nil to set to white
+    logger.dbg("CreDocument: set background color", bgcolor)
+    self._document:setBackgroundColor(bgcolor)
+end
+
 function CreDocument:setBackgroundImage(img_path) -- use nil to unset
     logger.dbg("CreDocument: set background image", img_path)
     self._document:setBackgroundImage(img_path)
@@ -941,6 +954,10 @@ function CreDocument:getStatistics()
     return self._document:getStatistics()
 end
 
+function CreDocument:getUnknownEntities()
+    return self._document:getUnknownEntities()
+end
+
 function CreDocument:canHaveAlternativeToc()
     return true
 end