diff --git a/firmware/fsm.c b/firmware/fsm.c
index b4025c5ee6..c0da402483 100644
--- a/firmware/fsm.c
+++ b/firmware/fsm.c
@@ -671,7 +671,7 @@ void fsm_msgSignIdentity(SignIdentity *msg)
 	const HDNode *node = fsm_getDerivedNode(address_n, 5);
 	if (!node) return;
 
-	uint8_t message[128];
+	uint8_t message[256 + 256];
 	memcpy(message, msg->challenge_hidden.bytes, msg->challenge_hidden.size);
 	const int len = strlen(msg->challenge_visual);
 	memcpy(message + msg->challenge_hidden.size, msg->challenge_visual, len);
diff --git a/firmware/protob/messages.options b/firmware/protob/messages.options
index da0af37c9c..a322f98601 100644
--- a/firmware/protob/messages.options
+++ b/firmware/protob/messages.options
@@ -86,8 +86,8 @@ EstimateTxSize.coin_name		max_size:17
 
 SignTx.coin_name			max_size:17
 
-SignIdentity.challenge_hidden		max_size:64
-SignIdentity.challenge_visual		max_size:64
+SignIdentity.challenge_hidden		max_size:256
+SignIdentity.challenge_visual		max_size:256
 
 SignedIdentity.address			max_size:36
 SignedIdentity.public_key		max_size:33
diff --git a/firmware/protob/messages.pb.h b/firmware/protob/messages.pb.h
index b56c8d37fa..b867cc947d 100644
--- a/firmware/protob/messages.pb.h
+++ b/firmware/protob/messages.pb.h
@@ -510,7 +510,7 @@ typedef struct _ResetDevice {
 
 typedef struct {
     size_t size;
-    uint8_t bytes[64];
+    uint8_t bytes[256];
 } SignIdentity_challenge_hidden_t;
 
 typedef struct _SignIdentity {
@@ -519,7 +519,7 @@ typedef struct _SignIdentity {
     bool has_challenge_hidden;
     SignIdentity_challenge_hidden_t challenge_hidden;
     bool has_challenge_visual;
-    char challenge_visual[64];
+    char challenge_visual[256];
 } SignIdentity;
 
 typedef struct {
@@ -975,7 +975,7 @@ extern const pb_field_t DebugLinkLog_fields[4];
 #define SimpleSignTx_size                        (19 + 0*TxInputType_size + 0*TxOutputType_size + 0*TransactionType_size)
 #define TxRequest_size                           (18 + TxRequestDetailsType_size + TxRequestSerializedType_size)
 #define TxAck_size                               (6 + TransactionType_size)
-#define SignIdentity_size                        (138 + IdentityType_size)
+#define SignIdentity_size                        (524 + IdentityType_size)
 #define SignedIdentity_size                      140
 #define FirmwareErase_size                       0
 #define FirmwareUpload_size                      2