diff --git a/.ci/after_success.sh b/.ci/after_success.sh
index 011b8d1be..2190d00e6 100755
--- a/.ci/after_success.sh
+++ b/.ci/after_success.sh
@@ -5,11 +5,6 @@ source "${CI_DIR}/common.sh"
 
 set +e
 
-travis_retry make coverage
-pushd koreader-*/koreader
-    luajit $(which luacov-coveralls) -v
-popd
-
 if [ ${TRAVIS_PULL_REQUEST} = false ] && [ ${TRAVIS_BRANCH} = 'master' ]; then
     travis_retry luarocks --local install ldoc
     # get deploy key for doc repo
@@ -36,7 +31,12 @@ if [ ${TRAVIS_PULL_REQUEST} = false ] && [ ${TRAVIS_BRANCH} = 'master' ]; then
     git -c user.name="KOReader build bot" -c user.email="non-reply@koreader.rocks" \
         commit -a --amend -m 'Automated documentation build from travis-ci.'
     git push -f --quiet origin gh-pages > /dev/null
-    echo -e "\n${ANSI_GREEN}Document update pushed."
+    echo -e "\n${ANSI_GREEN}Documentation update pushed."
 else
-    echo -e "\n${ANSI_GREEN}Not on official master branch, skip document update."
+    echo -e "\n${ANSI_GREEN}Not on official master branch, skip documentation update."
 fi
+
+travis_retry make coverage
+pushd koreader-*/koreader
+    luajit $(which luacov-coveralls)
+popd
diff --git a/frontend/apps/filemanager/filemanagermenu.lua b/frontend/apps/filemanager/filemanagermenu.lua
index e6025edfd..695307f0c 100644
--- a/frontend/apps/filemanager/filemanagermenu.lua
+++ b/frontend/apps/filemanager/filemanagermenu.lua
@@ -104,6 +104,7 @@ function FileManagerMenu:setUpdateItemTable()
         callback = function()
             local open_last = G_reader_settings:readSetting("open_last") or false
             G_reader_settings:saveSetting("open_last", not open_last)
+            G_reader_settings:flush()
         end
     })
     if Device.isKobo() then
@@ -121,6 +122,7 @@ function FileManagerMenu:setUpdateItemTable()
                             G_reader_settings:delSetting(
                                 "use_lastfile_as_screensaver")
                         end
+                        G_reader_settings:flush()
                     end
                 },
                 {
@@ -130,6 +132,7 @@ function FileManagerMenu:setUpdateItemTable()
                         local function save_folder_path()
                             G_reader_settings:saveSetting(
                                 "screensaver_folder", ss_folder_path_input:getInputText())
+                            G_reader_settings:flush()
                             UIManager:close(ss_folder_path_input)
                         end
                         local curr_path = G_reader_settings:readSetting("screensaver_folder")
diff --git a/frontend/apps/reader/modules/readerpaging.lua b/frontend/apps/reader/modules/readerpaging.lua
index 69931be91..8e012adee 100644
--- a/frontend/apps/reader/modules/readerpaging.lua
+++ b/frontend/apps/reader/modules/readerpaging.lua
@@ -10,6 +10,20 @@ local Math = require("optmath")
 local DEBUG = require("dbg")
 local _ = require("gettext")
 
+
+local function copyPageState(page_state)
+    return {
+        page = page_state.page,
+        zoom = page_state.zoom,
+        rotation = page_state.rotation,
+        gamma = page_state.gamma,
+        offset = page_state.offset:copy(),
+        visible_area = page_state.visible_area:copy(),
+        page_area = page_state.page_area:copy(),
+    }
+end
+
+
 local ReaderPaging = InputContainer:new{
     current_page = 0,
     number_of_pages = 0,
@@ -555,9 +569,12 @@ function ReaderPaging:getPrevPageState(blank_area, offset)
 end
 
 function ReaderPaging:updateTopPageState(state, blank_area, offset)
-    local visible_area = Geom:new{x = 0, y = 0}
-    visible_area.w, visible_area.h = blank_area.w, blank_area.h
-    visible_area.x, visible_area.y = state.visible_area.x, state.visible_area.y
+    local visible_area = Geom:new{
+        x = state.visible_area.x,
+        y = state.visible_area.y,
+        w = blank_area.w,
+        h = blank_area.h,
+    }
     if state.page == self.number_of_pages then
         visible_area:offsetWithin(state.page_area, offset.x, offset.y)
     else
@@ -566,14 +583,15 @@ function ReaderPaging:updateTopPageState(state, blank_area, offset)
     -- shrink blank area by the height of visible area
     blank_area.h = blank_area.h - visible_area.h
     state.visible_area = visible_area
-    return state
 end
 
 function ReaderPaging:updateBottomPageState(state, blank_area, offset)
-    local visible_area = Geom:new{x = 0, y = 0}
-    visible_area.w, visible_area.h = blank_area.w, blank_area.h
-    visible_area.x = state.page_area.x
-    visible_area.y = state.visible_area.y + state.visible_area.h - visible_area.h
+    local visible_area = Geom:new{
+        x = state.page_area.x,
+        y = state.visible_area.y + state.visible_area.h - blank_area.h,
+        w = blank_area.w,
+        h = blank_area.h,
+    }
     if state.page == 1 then
         visible_area:offsetWithin(state.page_area, offset.x, offset.y)
     else
@@ -582,7 +600,6 @@ function ReaderPaging:updateBottomPageState(state, blank_area, offset)
     -- shrink blank area by the height of visible area
     blank_area.h = blank_area.h - visible_area.h
     state.visible_area = visible_area
-    return state
 end
 
 function ReaderPaging:genPageStatesFromTop(top_page_state, blank_area, offset)
@@ -592,16 +609,18 @@ function ReaderPaging:genPageStatesFromTop(top_page_state, blank_area, offset)
     -- which will trigger the drawing of next page leaving part of current
     -- page undrawn. This should also be true for generating from bottom.
     if offset.y < 0 then offset.y = 0 end
-    local state = self:updateTopPageState(top_page_state, blank_area, offset)
+    self:updateTopPageState(top_page_state, blank_area, offset)
     local page_states = {}
-    if state.visible_area.h > 0 then
-        table.insert(page_states, state)
+    if top_page_state.visible_area.h > 0 then
+        -- offset does not scroll pass top_page_state
+        table.insert(page_states, top_page_state)
     end
-    local current_page = state.page
+    local state
+    local current_page = top_page_state.page
     while blank_area.h > 0 do
         blank_area.h = blank_area.h - self.view.page_gap.height
         if blank_area.h > 0 then
-            if self.current_page == self.number_of_pages then break end
+            if current_page == self.number_of_pages then break end
             self:_gotoPage(current_page + 1, "scrolling")
             current_page = current_page + 1
             state = self:getNextPageState(blank_area, Geom:new{})
@@ -614,16 +633,19 @@ end
 function ReaderPaging:genPageStatesFromBottom(bottom_page_state, blank_area, offset)
     -- scroll up offset should always be less than 0
     if offset.y > 0 then offset.y = 0 end
-    local state = self:updateBottomPageState(bottom_page_state, blank_area, offset)
+    -- find out number of pages need to be removed from current view
+    self:updateBottomPageState(bottom_page_state, blank_area, offset)
     local page_states = {}
-    if state.visible_area.h > 0 then
-        table.insert(page_states, state)
+    if bottom_page_state.visible_area.h > 0 then
+        table.insert(page_states, bottom_page_state)
     end
-    local current_page = state.page
+    -- fill up current view from bottom to top
+    local state
+    local current_page = bottom_page_state.page
     while blank_area.h > 0 do
         blank_area.h = blank_area.h - self.view.page_gap.height
         if blank_area.h > 0 then
-            if self.current_page == 1 then break end
+            if current_page == 1 then break end
             self:_gotoPage(current_page - 1, "scrolling")
             current_page = current_page - 1
             state = self:getPrevPageState(blank_area, Geom:new{})
@@ -634,29 +656,34 @@ function ReaderPaging:genPageStatesFromBottom(bottom_page_state, blank_area, off
 end
 
 function ReaderPaging:onScrollPanRel(diff)
+    if diff == 0 then return true end
     DEBUG("pan relative height:", diff)
+    local offset = Geom:new{x = 0, y = diff}
     local blank_area = Geom:new{}
     blank_area:setSizeTo(self.view.dimen)
+    local new_page_states
     if diff > 0 then
-        local first_page_state = table.remove(self.view.page_states, 1)
-        local offset = Geom:new{
-            x = 0,
-            y = diff,
-        }
-        self.view.page_states = self:genPageStatesFromTop(first_page_state, blank_area, offset)
-    end
-    if diff < 0 then
-        local last_page_state = table.remove(self.view.page_states)
-        local offset = Geom:new{
-            x = 0,
-            y = diff
-        }
-        self.view.page_states = self:genPageStatesFromBottom(last_page_state, blank_area, offset)
+        -- pan to scroll down
+        local first_page_state = copyPageState(self.view.page_states[1])
+        new_page_states = self:genPageStatesFromTop(
+            first_page_state, blank_area, offset)
+    elseif diff < 0 then
+        local last_page_state = copyPageState(
+            self.view.page_states[#self.view.page_states])
+        new_page_states = self:genPageStatesFromBottom(
+            last_page_state, blank_area, offset)
+    end
+    if #new_page_states == 0 then
+        -- if we are already at the top of first page or bottom of the last
+        -- page, new_page_states will be empty, in this case, nothing to update
+        return true
     end
+    self.view.page_states = new_page_states
     -- update current pageno to the very last part in current view
-    self:_gotoPage(self.view.page_states[#self.view.page_states].page, "scrolling")
-
+    self:_gotoPage(self.view.page_states[#self.view.page_states].page,
+                   "scrolling")
     UIManager:setDirty(self.view.dialog, "fast")
+    return true
 end
 
 function ReaderPaging:calculateOverlap()
@@ -664,8 +691,10 @@ function ReaderPaging:calculateOverlap()
     return self.overlap + footer_height
 end
 
-function ReaderPaging:onScrollPageRel(diff)
-    if diff > 0 then
+function ReaderPaging:onScrollPageRel(page_diff)
+    if page_diff == 0 then return true end
+    if page_diff > 0 then
+        -- page down, last page should be moved to top
         local last_page_state = table.remove(self.view.page_states)
         local last_visible_area = last_page_state.visible_area
         if last_page_state.page == self.number_of_pages and
@@ -683,7 +712,8 @@ function ReaderPaging:onScrollPageRel(diff)
             y = last_visible_area.h - overlap
         }
         self.view.page_states = self:genPageStatesFromTop(last_page_state, blank_area, offset)
-    elseif diff < 0 then
+    elseif page_diff < 0 then
+        -- page up, first page should be moved to bottom
         local blank_area = Geom:new{}
         blank_area:setSizeTo(self.view.dimen)
         local overlap = self:calculateOverlap()
@@ -692,9 +722,8 @@ function ReaderPaging:onScrollPageRel(diff)
             x = 0,
             y = -first_page_state.visible_area.h + overlap
         }
-        self.view.page_states = self:genPageStatesFromBottom(first_page_state, blank_area, offset)
-    else
-        return true
+        self.view.page_states = self:genPageStatesFromBottom(
+            first_page_state, blank_area, offset)
     end
     -- update current pageno to the very last part in current view
     self:_gotoPage(self.view.page_states[#self.view.page_states].page, "scrolling")
@@ -842,15 +871,16 @@ function ReaderPaging:onGotoPercentage(percentage)
 end
 
 function ReaderPaging:updateReadOrder()
+    local width, height = Screen:getWidth(), Screen:getHeight()
     if self.inverse_reading_order then
         self.ges_events.TapForward = {
             GestureRange:new{
                 ges = "tap",
                 range = Geom:new{
-                    x = Screen:getWidth()*(1-DTAP_ZONE_FORWARD.x-DTAP_ZONE_FORWARD.w),
-                    y = Screen:getHeight()*DTAP_ZONE_FORWARD.y,
-                    w = Screen:getWidth()*DTAP_ZONE_FORWARD.w,
-                    h = Screen:getHeight()*DTAP_ZONE_FORWARD.h,
+                    x = width * (1-DTAP_ZONE_FORWARD.x - DTAP_ZONE_FORWARD.w),
+                    y = height * DTAP_ZONE_FORWARD.y,
+                    w = width * DTAP_ZONE_FORWARD.w,
+                    h = height * DTAP_ZONE_FORWARD.h,
                 }
             }
         }
@@ -858,22 +888,22 @@ function ReaderPaging:updateReadOrder()
             GestureRange:new{
                 ges = "tap",
                 range = Geom:new{
-                    x = Screen:getWidth()*(1-DTAP_ZONE_BACKWARD.x-DTAP_ZONE_BACKWARD.w),
-                    y = Screen:getHeight()*DTAP_ZONE_BACKWARD.y,
-                    w = Screen:getWidth()*DTAP_ZONE_BACKWARD.w,
-                    h = Screen:getHeight()*DTAP_ZONE_BACKWARD.h,
+                    x = width * (1-DTAP_ZONE_BACKWARD.x - DTAP_ZONE_BACKWARD.w),
+                    y = height * DTAP_ZONE_BACKWARD.y,
+                    w = width * DTAP_ZONE_BACKWARD.w,
+                    h = height * DTAP_ZONE_BACKWARD.h,
                 }
             }
         }
     else
-                self.ges_events.TapForward = {
+        self.ges_events.TapForward = {
             GestureRange:new{
                 ges = "tap",
                 range = Geom:new{
-                    x = Screen:getWidth()*DTAP_ZONE_FORWARD.x,
-                    y = Screen:getHeight()*DTAP_ZONE_FORWARD.y,
-                    w = Screen:getWidth()*DTAP_ZONE_FORWARD.w,
-                    h = Screen:getHeight()*DTAP_ZONE_FORWARD.h,
+                    x = width * DTAP_ZONE_FORWARD.x,
+                    y = height * DTAP_ZONE_FORWARD.y,
+                    w = width * DTAP_ZONE_FORWARD.w,
+                    h = height * DTAP_ZONE_FORWARD.h,
                 }
             }
         }
@@ -881,10 +911,10 @@ function ReaderPaging:updateReadOrder()
             GestureRange:new{
                 ges = "tap",
                 range = Geom:new{
-                    x = Screen:getWidth()*DTAP_ZONE_BACKWARD.x,
-                    y = Screen:getHeight()*DTAP_ZONE_BACKWARD.y,
-                    w = Screen:getWidth()*DTAP_ZONE_BACKWARD.w,
-                    h = Screen:getHeight()*DTAP_ZONE_BACKWARD.h,
+                    x = width * DTAP_ZONE_BACKWARD.x,
+                    y = height * DTAP_ZONE_BACKWARD.y,
+                    w = width * DTAP_ZONE_BACKWARD.w,
+                    h = height * DTAP_ZONE_BACKWARD.h,
                 }
             }
         }
diff --git a/spec/unit/readerpaging_spec.lua b/spec/unit/readerpaging_spec.lua
index fb69a0aa8..42c94394c 100644
--- a/spec/unit/readerpaging_spec.lua
+++ b/spec/unit/readerpaging_spec.lua
@@ -1,18 +1,20 @@
 describe("Readerpaging module", function()
     local sample_pdf = "spec/front/unit/data/sample.pdf"
-    local readerui, UIManager, Event
+    local readerui, UIManager, Event, DocumentRegistry, ReaderUI
     local paging
 
     setup(function()
         require("commonrequire")
         UIManager = require("ui/uimanager")
         Event = require("ui/event")
+        DocumentRegistry = require("document/documentregistry")
+        ReaderUI = require("apps/reader/readerui")
     end)
 
     describe("Page mode", function()
         setup(function()
-            readerui = require("apps/reader/readerui"):new{
-                document = require("document/documentregistry"):openDocument(sample_pdf),
+            readerui = ReaderUI:new{
+                document = DocumentRegistry:openDocument(sample_pdf),
             }
             paging = readerui.paging
         end)
@@ -43,8 +45,8 @@ describe("Readerpaging module", function()
             purgeDir(DocSettings:getSidecarDir(sample_pdf))
             os.remove(DocSettings:getHistoryPath(sample_pdf))
 
-            readerui = require("apps/reader/readerui"):new{
-                document = require("document/documentregistry"):openDocument(sample_pdf),
+            readerui = ReaderUI:new{
+                document = DocumentRegistry:openDocument(sample_pdf),
             }
             paging = readerui.paging
         end)
@@ -68,5 +70,25 @@ describe("Readerpaging module", function()
             readerui.onEndOfBook = nil
             UIManager:quit()
         end)
+
+        it("should scroll withtout crash backward on the first page", function()
+            local sample_djvu = "spec/front/unit/data/djvu3spec.djvu"
+            local tmp_readerui = ReaderUI:new{
+                document = DocumentRegistry:openDocument(sample_djvu),
+            }
+            tmp_readerui.paging:onScrollPanRel(-100)
+        end)
+
+        it("should scroll withtout crash forward on the last page", function()
+            local sample_djvu = "spec/front/unit/data/djvu3spec.djvu"
+            local tmp_readerui = ReaderUI:new{
+                document = DocumentRegistry:openDocument(sample_djvu),
+            }
+            local paging = tmp_readerui.paging
+            paging:onGotoPage(tmp_readerui.document:getPageCount())
+            paging:onScrollPanRel(120)
+            paging:onScrollPanRel(-1)
+            paging:onScrollPanRel(120)
+        end)
     end)
 end)
diff --git a/spec/unit/readhistory_spec.lua b/spec/unit/readhistory_spec.lua
index 16942ecf8..11474e2db 100644
--- a/spec/unit/readhistory_spec.lua
+++ b/spec/unit/readhistory_spec.lua
@@ -272,7 +272,7 @@ describe("ReadHistory module", function()
         for i = 1, 500 do  -- at most 500 items are stored
             assert_item_is(h, i, string.format("%04d", i))
         end
-        
+
         for i = 1, 1000 do
             rm(to_file(i))
         end