diff --git a/lib/ansible/modules/cloud/amazon/ec2_win_password.py b/lib/ansible/modules/cloud/amazon/ec2_win_password.py
index 78268bc0ccb..ad7715defa1 100644
--- a/lib/ansible/modules/cloud/amazon/ec2_win_password.py
+++ b/lib/ansible/modules/cloud/amazon/ec2_win_password.py
@@ -133,7 +133,10 @@ def main():
 
     instance_id = module.params.get('instance_id')
     key_file = module.params.get('key_file')
-    b_key_passphrase = to_bytes(module.params.get('key_passphrase'), errors='surrogate_or_strict')
+    if module.params.get('key_passphrase') is None:
+        b_key_passphrase = None
+    else:
+        b_key_passphrase = to_bytes(module.params.get('key_passphrase'), errors='surrogate_or_strict')
     wait = module.params.get('wait')
     wait_timeout = int(module.params.get('wait_timeout'))