diff --git a/dangerzone/isolation_provider/container.py b/dangerzone/isolation_provider/container.py
index 0c3eb59be..27383ac6d 100644
--- a/dangerzone/isolation_provider/container.py
+++ b/dangerzone/isolation_provider/container.py
@@ -125,7 +125,7 @@ def is_available() -> bool:
         with subprocess.Popen(
             [container_runtime, "image", "ls"],
             stdout=subprocess.DEVNULL,
-            stderr=self.proc_stderr,
+            stderr=subprocess.PIPE,
             startupinfo=get_subprocess_startupinfo(),
         ) as p:
             _, stderr = p.communicate()
@@ -154,7 +154,7 @@ def exec(
             args,
             stdin=subprocess.PIPE,
             stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
+            stderr=self.proc_stderr,
             startupinfo=startupinfo,
             # Start the conversion process in a new session, so that we can later on
             # kill the process group, without killing the controlling script.