diff --git a/protob/messages-bitcoin.proto b/protob/messages-bitcoin.proto
index d44143314c..484a0f5b1a 100644
--- a/protob/messages-bitcoin.proto
+++ b/protob/messages-bitcoin.proto
@@ -56,7 +56,7 @@ message GetPublicKey {
  * @end
  */
 message PublicKey {
-    required hw.trezor.messages.common.HDNodeType node = 1;        // BIP32 public node
+    optional hw.trezor.messages.common.HDNodeType node = 1;        // BIP32 public node
     optional string xpub = 2;        // serialized form of public node
 }