diff --git a/archivebox/system.py b/archivebox/system.py
index 1d8cbdb0..698c89f6 100644
--- a/archivebox/system.py
+++ b/archivebox/system.py
@@ -18,7 +18,7 @@ from .config import PYTHON_BINARY, OUTPUT_PERMISSIONS
 
 
 
-def run(*args, input=None, capture_output=True, timeout=None, check=False, text=False, start_new_session=True, **kwargs):
+def run(cmd, *args, input=None, capture_output=True, timeout=None, check=False, text=False, start_new_session=True, **kwargs):
     """Patched of subprocess.run to kill forked child subprocesses and fix blocking io making timeout=innefective
         Mostly copied from https://github.com/python/cpython/blob/master/Lib/subprocess.py
     """
@@ -37,10 +37,10 @@ def run(*args, input=None, capture_output=True, timeout=None, check=False, text=
 
     pgid = None
     try:
-        if args[0].endswith('.py'):
-            args = (PYTHON_BINARY, *args)
+        if isinstance(cmd, (list, tuple)) and cmd[0].endswith('.py'):
+            cmd = (PYTHON_BINARY, *cmd)
 
-        with Popen(*args, start_new_session=start_new_session, **kwargs) as process:
+        with Popen(cmd, *args, start_new_session=start_new_session, **kwargs) as process:
             pgid = os.getpgid(process.pid)
             try:
                 stdout, stderr = process.communicate(input, timeout=timeout)