diff --git a/pkgs/development/python-modules/pexpect/default.nix b/pkgs/development/python-modules/pexpect/default.nix
index 651c48dbeb7b..aead62913c7b 100644
--- a/pkgs/development/python-modules/pexpect/default.nix
+++ b/pkgs/development/python-modules/pexpect/default.nix
@@ -2,9 +2,10 @@
 , buildPythonPackage
 , fetchPypi
 , ptyprocess
+, isPy3k
 }:
 
-buildPythonPackage rec {
+buildPythonPackage (rec {
   pname = "pexpect";
   version = "4.8.0";
 
@@ -40,4 +41,8 @@ buildPythonPackage rec {
       any platform that supports the standard Python pty module.
     '';
   };
-}
+# TODO: move into main set, this was to avoid a rebuild
+} // lib.optionalAttrs (!isPy3k ) {
+  # syntax error in _async module, likely intended only for Python 3.
+  dontUsePythonRecompileBytecode = !isPy3k;
+})