diff --git a/frontend/document/document.lua b/frontend/document/document.lua
index 535e09893..f274b6dda 100644
--- a/frontend/document/document.lua
+++ b/frontend/document/document.lua
@@ -1,11 +1,12 @@
+local TileCacheItem = require("document/tilecacheitem")
 local DrawContext = require("ffi/drawcontext")
+local Configurable = require("configurable")
 local Blitbuffer = require("ffi/blitbuffer")
-local Cache = require("cache")
+local lfs = require("libs/libkoreader-lfs")
 local CacheItem = require("cacheitem")
-local TileCacheItem = require("document/tilecacheitem")
 local Geom = require("ui/geometry")
-local Configurable = require("configurable")
 local Math = require("optmath")
+local Cache = require("cache")
 local DEBUG = require("dbg")
 
 --[[
@@ -114,6 +115,7 @@ function Document:getNativePageDimensions(pageno)
 end
 
 function Document:_readMetadata()
+    self.mod_time = lfs.attributes(self.file, "modification")
     self.info.number_of_pages = self._document:getPages()
     return true
 end
@@ -215,8 +217,13 @@ function Document:getCoverPageImage()
     return nil
 end
 
+function Document:getFullPageHash(pageno, zoom, rotation, gamma, render_mode)
+    return "renderpg|"..self.file.."|"..self.mod_time.."|"..pageno.."|"
+                    ..zoom.."|"..rotation.."|"..gamma.."|"..render_mode
+end
+
 function Document:renderPage(pageno, rect, zoom, rotation, gamma, render_mode)
-    local hash = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation.."|"..gamma.."|"..render_mode
+    local hash = self:getFullPageHash(pageno, zoom, rotation, gamma, render_mode)
     local page_size = self:getPageDimensions(pageno, zoom, rotation)
     -- this will be the size we actually render
     local size = page_size
@@ -231,12 +238,13 @@ function Document:renderPage(pageno, rect, zoom, rotation, gamma, render_mode)
             return
         end
         -- only render required part
-        hash = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation.."|"..gamma.."|"..render_mode.."|"..tostring(rect)
+        hash = self:getFullPageHash(pageno, zoom, rotation, gamma, render_mode).."|"..tostring(rect)
         size = rect
     end
 
     -- prepare cache item with contained blitbuffer
     local tile = TileCacheItem:new{
+        persistent = true,
         size = size.w * size.h + 64, -- estimation
         excerpt = size,
         pageno = pageno,
@@ -274,7 +282,7 @@ end
 -- a hint for the cache engine to paint a full page to the cache
 -- TODO: this should trigger a background operation
 function Document:hintPage(pageno, zoom, rotation, gamma, render_mode)
-    local hash_full_page = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation.."|"..gamma.."|"..render_mode
+    local hash_full_page = self:getFullPageHash(pageno, zoom, rotation, gamma, render_mode)
     if not Cache:check(hash_full_page, TileCacheItem) then
         DEBUG("hinting page", pageno)
         self:renderPage(pageno, nil, zoom, rotation, gamma, render_mode)
@@ -290,7 +298,7 @@ Draw page content to blitbuffer.
 @rect: visible_area inside document page
 --]]
 function Document:drawPage(target, x, y, rect, pageno, zoom, rotation, gamma, render_mode)
-    local hash_full_page = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation.."|"..gamma.."|"..render_mode
+    local hash_full_page = self:getFullPageHash(pageno, zoom, rotation, gamma, render_mode)
     local hash_excerpt = hash_full_page.."|"..tostring(rect)
     local tile = Cache:check(hash_full_page, TileCacheItem)
     if not tile then
diff --git a/frontend/document/koptinterface.lua b/frontend/document/koptinterface.lua
index 2193f5e29..368a78e37 100644
--- a/frontend/document/koptinterface.lua
+++ b/frontend/document/koptinterface.lua
@@ -107,7 +107,8 @@ function KoptInterface:getContextHash(doc, pageno, bbox)
     local screen_size = Screen:getSize()
     local screen_size_hash = screen_size.w.."|"..screen_size.h
     local bbox_hash = bbox.x0.."|"..bbox.y0.."|"..bbox.x1.."|"..bbox.y1
-    return doc.file.."|"..pageno.."|"..doc.configurable:hash("|").."|"..bbox_hash.."|"..screen_size_hash
+    return doc.file.."|"..doc.mod_time.."|"..pageno.."|"
+            ..doc.configurable:hash("|").."|"..bbox_hash.."|"..screen_size_hash
 end
 
 function KoptInterface:getPageBBox(doc, pageno)
@@ -215,6 +216,7 @@ function KoptInterface:getCachedContext(doc, pageno)
         DEBUG("reflowed page", pageno, "fullwidth:", fullwidth, "fullheight:", fullheight)
         self.last_context_size = fullwidth * fullheight + 128 -- estimation
         Cache:insert(kctx_hash, ContextCacheItem:new{
+            persistent = true,
             size = self.last_context_size,
             kctx = kc
         })
@@ -289,7 +291,7 @@ function KoptInterface:renderReflowedPage(doc, pageno, rect, zoom, rotation, ren
         end
         -- prepare cache item with contained blitbuffer
         local tile = TileCacheItem:new{
-            size = fullwidth * fullheight / 2 + 64, -- estimation
+            size = fullwidth * fullheight + 64, -- estimation
             excerpt = Geom:new{ w = fullwidth, h = fullheight },
             pageno = pageno,
         }
@@ -311,7 +313,7 @@ function KoptInterface:renderOptimizedPage(doc, pageno, rect, zoom, rotation, re
     local context_hash = self:getContextHash(doc, pageno, bbox)
     local renderpg_hash = "renderoptpg|"..context_hash..zoom
 
-    local cached = Cache:check(renderpg_hash)
+    local cached = Cache:check(renderpg_hash, TileCacheItem)
     if not cached then
         local page_size = Document.getNativePageDimensions(doc, pageno)
         local bbox = {
@@ -329,7 +331,8 @@ function KoptInterface:renderOptimizedPage(doc, pageno, rect, zoom, rotation, re
         local fullwidth, fullheight = kc:getPageDim()
         -- prepare cache item with contained blitbuffer
         local tile = TileCacheItem:new{
-            size = fullwidth * fullheight / 2 + 64, -- estimation
+            persistent = true,
+            size = fullwidth * fullheight + 64, -- estimation
             excerpt = Geom:new{
                 x = 0, y = 0,
                 w = fullwidth,