diff --git a/pkgs/tools/misc/expect/default.nix b/pkgs/tools/misc/expect/default.nix
index 6c9f348b8a1..9fcff332de6 100644
--- a/pkgs/tools/misc/expect/default.nix
+++ b/pkgs/tools/misc/expect/default.nix
@@ -14,8 +14,8 @@ stdenv.mkDerivation rec {
 
   hardeningDisable = [ "format" ];
 
-  preConfigure = ''
-    sed -i "s,/bin/stty,$(type -p stty),g" configure
+  postPatch = ''
+    sed -i "s,/bin/stty,$(type -p stty),g" configure.in
   '';
 
   configureFlags = [