diff --git a/pkgs/development/libraries/haskell/engine-io/default.nix b/pkgs/development/libraries/haskell/engine-io/default.nix
index 9684c7660fb..fd21d94cdf7 100644
--- a/pkgs/development/libraries/haskell/engine-io/default.nix
+++ b/pkgs/development/libraries/haskell/engine-io/default.nix
@@ -1,3 +1,5 @@
+# This file was auto-generated by cabal2nix. Please do NOT edit manually!
+
 { cabal, aeson, async, attoparsec, base64Bytestring, either
 , monadLoops, mwcRandom, stm, text, transformers
 , unorderedContainers, vector, websockets
diff --git a/pkgs/development/libraries/haskell/socket-io/default.nix b/pkgs/development/libraries/haskell/socket-io/default.nix
index ff0b90c03e0..a91832a0ad0 100644
--- a/pkgs/development/libraries/haskell/socket-io/default.nix
+++ b/pkgs/development/libraries/haskell/socket-io/default.nix
@@ -1,3 +1,5 @@
+# This file was auto-generated by cabal2nix. Please do NOT edit manually!
+
 { cabal, aeson, attoparsec, engineIo, mtl, stm, text, transformers
 , unorderedContainers, vector
 }: