diff --git a/pkgs/applications/misc/koreader/default.nix b/pkgs/applications/misc/koreader/default.nix
index 249569ffbab0..af66e2282b40 100644
--- a/pkgs/applications/misc/koreader/default.nix
+++ b/pkgs/applications/misc/koreader/default.nix
@@ -13,12 +13,12 @@
 let font-droid = nerdfonts.override { fonts = [ "DroidSansMono" ]; };
 in stdenv.mkDerivation rec {
   pname = "koreader";
-  version = "2021.03";
+  version = "2021.09";
 
   src = fetchurl {
     url =
       "https://github.com/koreader/koreader/releases/download/v${version}/koreader-${version}-amd64.deb";
-    sha256 = "sha256-XdCyx+SdcV1QitDVkOl9EZCHpU8Qiwu0qhcXkU6b+9o=";
+    sha256 = "1q2mbmczx2y5ylriq4k3lbjlpw4pwfq2vvcx06ymax31fsrvix84";
   };
 
   sourceRoot = ".";