diff --git a/xpra/server/server_util.py b/xpra/server/server_util.py
index 2ff2c0c..513201a 100644
--- a/xpra/server/server_util.py
+++ b/xpra/server/server_util.py
@@ -17,6 +17,10 @@ if PYTHON3:
         return b"'" + s.replace(b"'", b"'\\''") + b"'"
     
     def xpra_runner_shell_script(xpra_file, starting_dir, socket_dir):
+        # Nixpkgs contortion:
+        # xpra_file points to a shell wrapper, not to the python script.
+        dirname, basename = os.path.split(xpra_file)
+        xpra_file = os.path.join(dirname, "."+basename+"-wrapped")
         script = []
         script.append(b"#!/bin/sh\n")
         for var, value in os.environb.items():