diff --git a/common/protob/messages-binance.proto b/common/protob/messages-binance.proto
index 0483e548a..d02076ff8 100644
--- a/common/protob/messages-binance.proto
+++ b/common/protob/messages-binance.proto
@@ -21,7 +21,7 @@ message BinanceGetAddress {
  * @end
  */
 message BinanceAddress {
-    optional string address = 1;    // prefixed bech32 Binance address
+    required string address = 1;    // prefixed bech32 Binance address
 }
 
 /**
@@ -39,7 +39,7 @@ message BinanceGetPublicKey {
  * @end
  */
 message BinancePublicKey {
-    optional bytes public_key = 1;
+    required bytes public_key = 1;
 }
 
 /**
@@ -141,7 +141,7 @@ message BinanceCancelMsg {
  * @end
  */
 message BinanceSignedTx {
-	optional bytes signature = 1;
-    optional bytes public_key = 2;
+	required bytes signature = 1;
+    required bytes public_key = 2;
 }
 
diff --git a/common/protob/messages-bitcoin.proto b/common/protob/messages-bitcoin.proto
index 73021fb30..2bc64026c 100644
--- a/common/protob/messages-bitcoin.proto
+++ b/common/protob/messages-bitcoin.proto
@@ -80,8 +80,8 @@ message GetPublicKey {
  * @end
  */
 message PublicKey {
-    optional common.HDNodeType node = 1;        // BIP32 public node
-    optional string xpub = 2;                   // serialized form of public node
+    required common.HDNodeType node = 1;        // BIP32 public node
+    required string xpub = 2;                   // serialized form of public node
     optional uint32 root_fingerprint = 3;       // master root node fingerprint
 }
 
@@ -147,8 +147,8 @@ message SignMessage {
  * @end
  */
 message MessageSignature {
-    optional string address = 1;    // address used to sign the message
-    optional bytes signature = 2;   // signature of the message
+    required string address = 1;    // address used to sign the message
+    required bytes signature = 2;   // signature of the message
 }
 
 /**
diff --git a/common/protob/messages-common.proto b/common/protob/messages-common.proto
index 7f1fdc43a..2790cf2bc 100644
--- a/common/protob/messages-common.proto
+++ b/common/protob/messages-common.proto
@@ -10,7 +10,7 @@ option java_outer_classname = "TrezorMessageCommon";
  * @end
  */
 message Success {
-    optional string message = 1;    // human readable description of action or request-specific payload
+    optional string message = 1 [default=""]; // human readable description of action or request-specific payload
 }
 
 /**
diff --git a/common/protob/messages-crypto.proto b/common/protob/messages-crypto.proto
index 911b8b7db..55a0df479 100644
--- a/common/protob/messages-crypto.proto
+++ b/common/protob/messages-crypto.proto
@@ -123,5 +123,5 @@ message CosiSign {
  * @end
  */
 message CosiSignature {
-    optional bytes signature = 1;   // Signature
+    required bytes signature = 1;   // Signature
 }
diff --git a/common/protob/messages-eos.proto b/common/protob/messages-eos.proto
index 445098085..1e455164b 100644
--- a/common/protob/messages-eos.proto
+++ b/common/protob/messages-eos.proto
@@ -21,8 +21,8 @@ message EosGetPublicKey {
  * @end
  */
 message EosPublicKey {
-    optional string wif_public_key = 1; // EOS pub key in Base58 encoding
-    optional bytes raw_public_key = 2;  // Raw public key
+    required string wif_public_key = 1; // EOS pub key in Base58 encoding
+    required bytes raw_public_key = 2;  // Raw public key
 }
 
 /**
@@ -101,10 +101,10 @@ message EosTxActionAck {
      * Structure representing auth key
      */
     message EosAuthorizationKey {
-        optional uint32 type = 1;
+        required uint32 type = 1;
         optional bytes key = 2;        // Explicit public key bytes; when present, address_n must be empty
         repeated uint32 address_n = 3; // BIP-32 path to derive key; when filled out, key must not be present
-        optional uint32 weight = 4;
+        required uint32 weight = 4;
     }
 
     /**
@@ -266,7 +266,7 @@ message EosTxActionAck {
      * Structure representing actions not implemented above.
      */
     message EosActionUnknown {
-        optional uint32 data_size = 1;
+        required uint32 data_size = 1;
         optional bytes data_chunk = 2;
     }
 }
@@ -277,5 +277,5 @@ message EosTxActionAck {
  * @end
  */
 message EosSignedTx {
-    optional string signature = 1; // Computed signature
+    required string signature = 1; // Computed signature
 }
diff --git a/common/protob/messages-ethereum.proto b/common/protob/messages-ethereum.proto
index 2a62ce114..9fab13c2c 100644
--- a/common/protob/messages-ethereum.proto
+++ b/common/protob/messages-ethereum.proto
@@ -24,8 +24,8 @@ message EthereumGetPublicKey {
  * @end
  */
 message EthereumPublicKey {
-    optional hw.trezor.messages.common.HDNodeType node = 1;        // BIP32 public node
-    optional string xpub = 2;        // serialized form of public node
+    required hw.trezor.messages.common.HDNodeType node = 1;        // BIP32 public node
+    required string xpub = 2;        // serialized form of public node
 }
 
 /**
@@ -107,8 +107,8 @@ message EthereumSignMessage {
  * @end
  */
 message EthereumMessageSignature {
-    optional bytes signature = 2;   // signature of the message
-    optional string address = 3;     // address used to sign the message
+    required bytes signature = 2;   // signature of the message
+    required string address = 3;     // address used to sign the message
 }
 
 /**
diff --git a/common/protob/messages-lisk.proto b/common/protob/messages-lisk.proto
index b91cd9950..ee7d78083 100644
--- a/common/protob/messages-lisk.proto
+++ b/common/protob/messages-lisk.proto
@@ -21,7 +21,7 @@ message LiskGetAddress {
  * @end
  */
 message LiskAddress {
-    optional string address = 1;    // Lisk address
+    required string address = 1;    // Lisk address
 }
 
 /**
@@ -39,7 +39,7 @@ message LiskGetPublicKey {
  * @end
  */
 message LiskPublicKey {
-    optional bytes public_key = 1;  // Lisk public key
+    required bytes public_key = 1;  // Lisk public key
 }
 
 /**
@@ -50,7 +50,7 @@ message LiskPublicKey {
  */
 message LiskSignTx {
     repeated uint32 address_n = 1;                  // BIP-32 path to derive the key from master node
-    optional LiskTransactionCommon transaction = 2; // Lisk transaction structure
+    required LiskTransactionCommon transaction = 2; // Lisk transaction structure
     /**
      * Structure representing the common part for Lisk transactions
      */
@@ -115,7 +115,7 @@ message LiskSignTx {
  * @end
  */
 message LiskSignedTx {
-    optional bytes signature = 1;
+    required bytes signature = 1;
 }
 
 /**
@@ -126,7 +126,7 @@ message LiskSignedTx {
  */
 message LiskSignMessage {
     repeated uint32 address_n = 1;
-    optional bytes message = 2;
+    required bytes message = 2;
 }
 
 /**
@@ -134,8 +134,8 @@ message LiskSignMessage {
  * @end
  */
 message LiskMessageSignature {
-    optional bytes public_key = 1;
-    optional bytes signature = 2;
+    required bytes public_key = 1;
+    required bytes signature = 2;
 }
 
 /**
@@ -145,7 +145,7 @@ message LiskMessageSignature {
  * @next Failure
  */
 message LiskVerifyMessage {
-    optional bytes public_key = 1;
-    optional bytes signature = 2;
-    optional bytes message = 3;
+    required bytes public_key = 1;
+    required bytes signature = 2;
+    required bytes message = 3;
 }
diff --git a/common/protob/messages-management.proto b/common/protob/messages-management.proto
index b9f8a61fd..790f400d2 100644
--- a/common/protob/messages-management.proto
+++ b/common/protob/messages-management.proto
@@ -46,9 +46,9 @@ message GetFeatures {
  */
 message Features {
     optional string vendor = 1;                 // name of the manufacturer, e.g. "trezor.io"
-    optional uint32 major_version = 2;          // major version of the firmware/bootloader, e.g. 1
-    optional uint32 minor_version = 3;          // minor version of the firmware/bootloader, e.g. 0
-    optional uint32 patch_version = 4;          // patch version of the firmware/bootloader, e.g. 0
+    required uint32 major_version = 2;          // major version of the firmware/bootloader, e.g. 1
+    required uint32 minor_version = 3;          // minor version of the firmware/bootloader, e.g. 0
+    required uint32 patch_version = 4;          // patch version of the firmware/bootloader, e.g. 0
     optional bool bootloader_mode = 5;          // is device in bootloader mode?
     optional string device_id = 6;              // device's unique identifier
     optional bool pin_protection = 7;           // is device protected by PIN?
@@ -196,7 +196,7 @@ message SdProtect {
  * @next Success
  */
 message Ping {
-    optional string message = 1;                // message to send back in Success message
+    optional string message = 1 [default=""];   // message to send back in Success message
     optional bool button_protection = 2;        // ask for button press
 }
 
diff --git a/common/protob/messages-nem.proto b/common/protob/messages-nem.proto
index 295f9dcdb..e65f2c965 100644
--- a/common/protob/messages-nem.proto
+++ b/common/protob/messages-nem.proto
@@ -172,8 +172,8 @@ message NEMSignTx {
  * @end
  */
 message NEMSignedTx {
-    optional bytes data = 1;        // Transaction data
-    optional bytes signature = 2;   // Signature for the transaction
+    required bytes data = 1;        // Transaction data
+    required bytes signature = 2;   // Signature for the transaction
 }
 
 /**
@@ -194,5 +194,5 @@ message NEMDecryptMessage {
  * @end
  */
 message NEMDecryptedMessage {
-    optional bytes payload = 1;     // Actual message data (unencrypted)
+    required bytes payload = 1;     // Actual message data (unencrypted)
 }
diff --git a/common/protob/messages-ripple.proto b/common/protob/messages-ripple.proto
index 5edc2babb..5bb661785 100644
--- a/common/protob/messages-ripple.proto
+++ b/common/protob/messages-ripple.proto
@@ -20,7 +20,7 @@ message RippleGetAddress {
  * @end
  */
 message RippleAddress {
-    optional string address = 1;                // Address in Ripple format (base58 of a pubkey with checksum)
+    required string address = 1;                // Address in Ripple format (base58 of a pubkey with checksum)
 }
 
 /**
@@ -43,8 +43,8 @@ message RippleSignTx {
      * - see https://developers.ripple.com/payment.html
      */
     message RipplePayment {
-        optional uint64 amount = 1;             // only XRP is supported at the moment so this an integer
-        optional string destination = 2;        // destination account address
+        required uint64 amount = 1;             // only XRP is supported at the moment so this an integer
+        required string destination = 2;        // destination account address
         optional uint32 destination_tag = 3;    // destination tag to identify payments
     }
 }
@@ -54,6 +54,6 @@ message RippleSignTx {
  * @end
  */
 message RippleSignedTx {
-    optional bytes signature = 1;
-    optional bytes serialized_tx = 2;
+    required bytes signature = 1;
+    required bytes serialized_tx = 2;
 }
diff --git a/common/protob/messages-stellar.proto b/common/protob/messages-stellar.proto
index c8229c7c0..8587b9e0b 100644
--- a/common/protob/messages-stellar.proto
+++ b/common/protob/messages-stellar.proto
@@ -10,7 +10,7 @@ option java_outer_classname = "TrezorMessageStellar";
  * @embed
  */
 message StellarAssetType {
-    optional uint32 type = 1;       // 0 = native asset (XLM), 1 = alphanum 4, 2 = alphanum 12
+    required uint32 type = 1;       // 0 = native asset (XLM), 1 = alphanum 4, 2 = alphanum 12
     optional string code = 2;       // for non-native assets, string describing the code
     optional string issuer = 3;     // issuing address
 }
@@ -30,7 +30,7 @@ message StellarGetAddress {
  * @end
  */
 message StellarAddress {
-    optional string address = 1;    // Address in Stellar format (base32 of a pubkey with checksum)
+    required string address = 1;    // Address in Stellar format (base32 of a pubkey with checksum)
 }
 
 /**
@@ -217,6 +217,6 @@ message StellarBumpSequenceOp {
  * @end
  */
 message StellarSignedTx {
-    optional bytes public_key = 1;  // public key for the private key used to sign data
-    optional bytes signature = 2;   // signature suitable for sending to the Stellar network
+    required bytes public_key = 1;  // public key for the private key used to sign data
+    required bytes signature = 2;   // signature suitable for sending to the Stellar network
 }
diff --git a/common/protob/messages-tezos.proto b/common/protob/messages-tezos.proto
index 474f18628..51e29151f 100644
--- a/common/protob/messages-tezos.proto
+++ b/common/protob/messages-tezos.proto
@@ -21,7 +21,7 @@ message TezosGetAddress {
  * @end
  */
 message TezosAddress {
-    optional string address = 1;        // Coin address in Base58 encoding
+    required string address = 1;        // Coin address in Base58 encoding
 }
 
 /**
@@ -39,7 +39,7 @@ message TezosGetPublicKey {
  * @end
  */
 message TezosPublicKey {
-    optional string public_key = 1;          // b58 encoded Tezos public key with prefix
+    required string public_key = 1;          // b58 encoded Tezos public key with prefix
 }
 
 /**
@@ -49,7 +49,7 @@ message TezosPublicKey {
  */
 message TezosSignTx {
     repeated uint32 address_n = 1;                  // BIP-32 path to derive the key from master node
-    optional bytes branch = 2;
+    required bytes branch = 2;
 
     optional TezosRevealOp reveal = 3;              // Tezos reveal operation (may be bundled with other op)
     optional TezosTransactionOp transaction = 4;    // Tezos transaction operation
@@ -61,8 +61,8 @@ message TezosSignTx {
      * Tezos contract ID
      */
     message TezosContractID {
-        optional TezosContractType tag = 1;
-        optional bytes hash = 2;                    // Implicit = 21B, originated = 20B + 1B padding
+        required TezosContractType tag = 1;
+        required bytes hash = 2;                    // Implicit = 21B, originated = 20B + 1B padding
         /*
          * Type of Tezos Contract type
          */
@@ -75,24 +75,24 @@ message TezosSignTx {
      * Structure representing information for reveal
      */
     message TezosRevealOp {
-        optional bytes source = 7;
-        optional uint64 fee = 2;
-        optional uint64 counter = 3;
-        optional uint64 gas_limit = 4;
-        optional uint64 storage_limit = 5;
-        optional bytes public_key = 6;
+        required bytes source = 7;
+        required uint64 fee = 2;
+        required uint64 counter = 3;
+        required uint64 gas_limit = 4;
+        required uint64 storage_limit = 5;
+        required bytes public_key = 6;
     }
     /**
      * Structure representing information for transaction
      */
     message TezosTransactionOp {
-        optional bytes source = 9;
-        optional uint64 fee = 2;
-        optional uint64 counter = 3;
-        optional uint64 gas_limit = 4;
-        optional uint64 storage_limit = 5;
-        optional uint64 amount = 6;
-        optional TezosContractID destination = 7;
+        required bytes source = 9;
+        required uint64 fee = 2;
+        required uint64 counter = 3;
+        required uint64 gas_limit = 4;
+        required uint64 storage_limit = 5;
+        required uint64 amount = 6;
+        required TezosContractID destination = 7;
         optional bytes parameters = 8;
         optional TezosParametersManager parameters_manager = 10;
 
@@ -111,28 +111,28 @@ message TezosSignTx {
      * Structure representing information for origination
      */
     message TezosOriginationOp {
-        optional bytes source = 12;
-        optional uint64 fee = 2;
-        optional uint64 counter = 3;
-        optional uint64 gas_limit = 4;
-        optional uint64 storage_limit = 5;
+        required bytes source = 12;
+        required uint64 fee = 2;
+        required uint64 counter = 3;
+        required uint64 gas_limit = 4;
+        required uint64 storage_limit = 5;
         optional bytes manager_pubkey = 6;
-        optional uint64 balance = 7;
+        required uint64 balance = 7;
         optional bool spendable = 8;
         optional bool delegatable = 9;
         optional bytes delegate = 10;
-        optional bytes script = 11;
+        required bytes script = 11;
     }
     /**
      * Structure representing information for delegation
      */
     message TezosDelegationOp {
-        optional bytes source = 7;
-        optional uint64 fee = 2;
-        optional uint64 counter = 3;
-        optional uint64 gas_limit = 4;
-        optional uint64 storage_limit = 5;
-        optional bytes delegate = 6;
+        required bytes source = 7;
+        required uint64 fee = 2;
+        required uint64 counter = 3;
+        required uint64 gas_limit = 4;
+        required uint64 storage_limit = 5;
+        required bytes delegate = 6;
     }
     /**
      * Structure representing information for proposal
@@ -164,7 +164,7 @@ message TezosSignTx {
  * @end
  */
 message TezosSignedTx {
-    optional string signature = 1;          // Tezos b58 encoded transaction signature with prefix
-    optional bytes sig_op_contents = 2;     // operation_bytes + signed operation_bytes
-    optional string operation_hash = 3;     // b58 encoded hashed operation contents with prefix
+    required string signature = 1;          // Tezos b58 encoded transaction signature with prefix
+    required bytes sig_op_contents = 2;     // operation_bytes + signed operation_bytes
+    required string operation_hash = 3;     // b58 encoded hashed operation contents with prefix
 }