diff --git a/defaults.lua b/defaults.lua
index 227269562..7ede43242 100644
--- a/defaults.lua
+++ b/defaults.lua
@@ -96,8 +96,8 @@ DKOPTREADER_CONFIG_MAX_COLUMNS = 2        -- range from 1 to 4
 DKOPTREADER_CONFIG_CONTRAST = 1.0        -- range from 0.2 to 2.0
 
 -- word spacing for reflow
-DKOPTREADER_CONFIG_WORD_SAPCINGS = {0.05, -1, 0.375}    -- range from 0.05 to 0.5
-DKOPTREADER_CONFIG_DEFAULT_WORD_SAPCING = -1            -- range from 0.05 to 0.5
+DKOPTREADER_CONFIG_WORD_SPACINGS = {0.05, -0.2, 0.375}    -- range from (+/-)0.05 to (+/-)0.5
+DKOPTREADER_CONFIG_DEFAULT_WORD_SPACING = -0.2            -- range from (+/-)0.05 to (+/-)0.5
 -- document languages for OCR
 DKOPTREADER_CONFIG_DOC_LANGS_TEXT = {"English", "Chinese"}
 DKOPTREADER_CONFIG_DOC_LANGS_CODE = {"eng", "chi_sim"}    -- language code, make sure you have corresponding training data
diff --git a/frontend/apps/reader/modules/readerkoptlistener.lua b/frontend/apps/reader/modules/readerkoptlistener.lua
index d7812e8b3..5b66b6e77 100644
--- a/frontend/apps/reader/modules/readerkoptlistener.lua
+++ b/frontend/apps/reader/modules/readerkoptlistener.lua
@@ -20,6 +20,11 @@ function ReaderKoptListener:onReadSettings(config)
     self.document.configurable.contrast = config:readSetting("kopt_contrast") or
                     G_reader_settings:readSetting("kopt_contrast") or 1.0
     self.ui:handleEvent(Event:new("GammaUpdate", 1/self.document.configurable.contrast))
+    -- since K2pdfopt v2.21 negative value of word spacing is also used, for config
+    -- compatability we should manually change previous -1 to a more reasonable -0.2
+    if self.document.configurable.word_spacing == -1 then
+        self.document.configurable.word_spacing = -0.2
+    end
 end
 
 function ReaderKoptListener:onSaveSettings()
diff --git a/frontend/ui/data/koptoptions.lua b/frontend/ui/data/koptoptions.lua
index 8c1b36306..685611928 100644
--- a/frontend/ui/data/koptoptions.lua
+++ b/frontend/ui/data/koptoptions.lua
@@ -186,8 +186,8 @@ local KoptOptions = {
                 name = "word_spacing",
                 name_text = S.WORD_GAP,
                 toggle = {S.SMALL, S.AUTO, S.LARGE},
-                values = DKOPTREADER_CONFIG_WORD_SAPCINGS,
-                default_value = DKOPTREADER_CONFIG_DEFAULT_WORD_SAPCING,
+                values = DKOPTREADER_CONFIG_WORD_SPACINGS,
+                default_value = DKOPTREADER_CONFIG_DEFAULT_WORD_SPACING,
             },
             {
                 name = "writing_direction",
diff --git a/koreader-base b/koreader-base
index 3dc42b01b..32dae406a 160000
--- a/koreader-base
+++ b/koreader-base
@@ -1 +1 @@
-Subproject commit 3dc42b01bc52701dd3682f32b64d1498b28b895b
+Subproject commit 32dae406abd6667e3ff0793c8d09584d21ca5693