diff --git a/bw_add_sshkeys.py b/bw_add_sshkeys.py
index 0a8320e..f270eb7 100755
--- a/bw_add_sshkeys.py
+++ b/bw_add_sshkeys.py
@@ -205,10 +205,10 @@ def ssh_add(session: str, item_id: str, key_id: str, key_pw: str = "") -> None:
     # CAVEAT: `ssh-add` provides no useful output, even with maximum verbosity
     subprocess.run(
         ["ssh-add", "-"],
-        input=ssh_key,
+        input=ssh_key.encode("utf-8"),
         # Works even if ssh-askpass is not installed
         env=envdict,
-        universal_newlines=True,
+        universal_newlines=False,
         check=True,
     )