diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index dcdcd0387f..ea5c3c5162 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -101,9 +101,8 @@ def qemu_tool_pipe_and_status(tool: str, args: Sequence[str],
                             universal_newlines=True)
     output = subp.communicate()[0]
     if subp.returncode < 0:
-        sys.stderr.write('%s received signal %i: %s\n'
-                         % (tool, -subp.returncode,
-                            ' '.join(qemu_img_args + list(args))))
+        cmd = ' '.join(args)
+        sys.stderr.write(f'{tool} received signal {-subp.returncode}: {cmd}\n')
     return (output, subp.returncode)
 
 def qemu_img_pipe_and_status(*args: str) -> Tuple[str, int]: