diff --git a/xpra/server/server_util.py b/xpra/server/server_util.py
index dd7c7c1..066b9ff 100644
--- a/xpra/server/server_util.py
+++ b/xpra/server/server_util.py
@@ -37,6 +37,10 @@ def sh_quotemeta(s):
     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():