diff --git a/src/ssh/Input.cxx b/src/ssh/Input.cxx
index 2c28b9f..b424528 100644
--- a/src/ssh/Input.cxx
+++ b/src/ssh/Input.cxx
@@ -183,11 +183,11 @@ Input::ReadUnencryptedPacket()
 inline std::span<const std::byte>
 Input::ReadDecryptedPacket()
 {
+	const std::scoped_lock lock{mutex};
+
 	if (error)
 		std::rethrow_exception(error);
 
-	const std::scoped_lock lock{mutex};
-
 	if (decrypted_list.empty()) {
 		/* if there was a NEWKEYS packet, it must have been
 		   handled by now and SetCipher() must have been