diff --git a/pkgs/development/libraries/haskell/engine-io/default.nix b/pkgs/development/libraries/haskell/engine-io/default.nix
index 7632ee316667..141d54ab23c8 100644
--- a/pkgs/development/libraries/haskell/engine-io/default.nix
+++ b/pkgs/development/libraries/haskell/engine-io/default.nix
@@ -1,17 +1,17 @@
 # This file was auto-generated by cabal2nix. Please do NOT edit manually!
 
 { cabal, aeson, async, attoparsec, base64Bytestring, either, free
-, monadLoops, mwcRandom, stm, text, transformers
+, monadLoops, mwcRandom, stm, stmDelay, text, transformers
 , unorderedContainers, vector, websockets
 }:
 
 cabal.mkDerivation (self: {
   pname = "engine-io";
-  version = "1.2.1";
-  sha256 = "17zyl61qdxrsxy7xiqkrl3pp40hhv76gndsi30p00468a6nbk0z6";
+  version = "1.2.2";
+  sha256 = "1d8323nxklbhva2y8ymgm5h57j2p86sdjfh0yi1fjjr8p26dh2py";
   buildDepends = [
     aeson async attoparsec base64Bytestring either free monadLoops
-    mwcRandom stm text transformers unorderedContainers vector
+    mwcRandom stm stmDelay text transformers unorderedContainers vector
     websockets
   ];
   meta = {