diff --git a/contracts/EvolveProxy.sol b/contracts/EvolveProxy.sol
index 19e469f..b121f5a 100644
--- a/contracts/EvolveProxy.sol
+++ b/contracts/EvolveProxy.sol
@@ -58,6 +58,12 @@ contract EvolveProxy is Ownable, Initializable, HasSignature {
             tokenIds[0] > 0 && tokenIds[1] > 0, 
             "EvolveProxy: hero to evolve and burn can not be 0"
         );
+
+        require(
+            tokenIds[0] != tokenIds[1],
+            "EvolveProxy: hero to evolve and burn can not be same"
+        );
+        
         require(
             hero.ownerOf(tokenIds[0]) == msg.sender, 
             "EvolveProxy: not owner of this hero now"
@@ -97,6 +103,11 @@ contract EvolveProxy is Ownable, Initializable, HasSignature {
             "EvolveProxy: equip to evolve and burn can not be 0"
         );
 
+        require(
+            tokenIds[0] != tokenIds[1],
+            "EvolveProxy: equip to evolve and burn can not be same"
+        );
+
         require(
             equip.ownerOf(tokenIds[0]) == msg.sender, 
             "EvolveProxy: current address is not owner of this equip now"
diff --git a/contracts/HasSignature.sol b/contracts/HasSignature.sol
index 9bbd1cf..fd49534 100644
--- a/contracts/HasSignature.sol
+++ b/contracts/HasSignature.sol
@@ -92,7 +92,7 @@ contract HasSignature {
         address signer,
         bytes32 structHash,
         bytes memory signature 
-    ) external view{
+    ) public view{
         bytes32 digest = _hashTypedDataV4(structHash);
         address recovered = ECDSA.recover(digest, signature);
         require(recovered == signer, "[BE] invalid signature");
@@ -103,7 +103,7 @@ contract HasSignature {
         address signer,
         bytes32 hash,
         bytes memory signature 
-    ) external pure {
+    ) public pure {
         require(signature.length == 65, "[BE] invalid signature length");
         bytes32 ethSignedMessageHash = ECDSA.toEthSignedMessageHash(
             hash