diff --git a/firmware/fsm_msg_coin.h b/firmware/fsm_msg_coin.h
index 4f086a5e73..2eb8e3a574 100644
--- a/firmware/fsm_msg_coin.h
+++ b/firmware/fsm_msg_coin.h
@@ -209,6 +209,8 @@ void fsm_msgGetAddress(GetAddress *msg)
 
 void fsm_msgSignMessage(SignMessage *msg)
 {
+	// CHECK_PARAM(is_ascii_only(msg->message.bytes, msg->message.size), _("Cannot sign non-ASCII strings"));
+
 	RESP_INIT(MessageSignature);
 
 	CHECK_INITIALIZED
diff --git a/firmware/layout2.c b/firmware/layout2.c
index 5f8a4ab37d..7ad7e27aac 100644
--- a/firmware/layout2.c
+++ b/firmware/layout2.c
@@ -296,17 +296,20 @@ void layoutConfirmOutput(const CoinInfo *coin, const TxAck_TransactionType_TxOut
 	render_address_dialog(coin, address, _("Confirm sending"), str_out, extra_line);
 }
 
-void layoutConfirmOpReturn(const uint8_t *data, uint32_t size)
+bool is_valid_ascii(const uint8_t *data, uint32_t size)
 {
-	bool ascii_only = true;
 	for (uint32_t i = 0; i < size; i++) {
 		if (data[i] < ' ' || data[i] > '~') {
-			ascii_only = false;
-			break;
+			return false;
 		}
 	}
+	return true;
+}
+
+void layoutConfirmOpReturn(const uint8_t *data, uint32_t size)
+{
 	const char **str;
-	if (!ascii_only) {
+	if (!is_valid_ascii(data, size)) {
 		char hex[65];
 		memset(hex, 0, sizeof(hex));
 		data2hex(data, (size > 32) ? 32 : size, hex);
diff --git a/firmware/layout2.h b/firmware/layout2.h
index b41a1546bd..5c38ad5c22 100644
--- a/firmware/layout2.h
+++ b/firmware/layout2.h
@@ -72,5 +72,6 @@ void layoutNEMLevy(const NEMSignTx_NEMMosaicCreation_NEMMosaicDefinition *defini
 void layoutCosiCommitSign(const uint32_t *address_n, size_t address_n_count, const uint8_t *data, uint32_t len, bool final_sign);
 
 const char **split_message(const uint8_t *msg, uint32_t len, uint32_t rowlen);
+bool is_valid_ascii(const uint8_t *data, uint32_t size);
 
 #endif