diff --git a/owrx/wsjt.py b/owrx/wsjt.py
index 16d1a73..4818201 100644
--- a/owrx/wsjt.py
+++ b/owrx/wsjt.py
@@ -149,10 +149,9 @@ class WsjtChopper(threading.Thread):
 
     def decode(self, file):
         decoder = subprocess.Popen(
-            self.decoder_commandline(file),
+            ["nice", "-n", "10"] + self.decoder_commandline(file),
             stdout=subprocess.PIPE,
             cwd=self.tmp_dir,
-            preexec_fn=lambda: os.nice(10),
             close_fds=True,
         )
         for line in decoder.stdout: