diff --git a/contracts/lib/MerklePatriciaProof.sol b/contracts/lib/MerklePatriciaProof.sol
index febd8c05..bcf4a385 100644
--- a/contracts/lib/MerklePatriciaProof.sol
+++ b/contracts/lib/MerklePatriciaProof.sol
@@ -69,17 +69,16 @@ library MerklePatriciaProof {
                 );
                 pathPtr += 1;
             } else if (currentNodeList.length == 2) {
-                // Alternative 1 start
                 bytes memory nodeValue = RLPReader.toBytes(currentNodeList[0]);
                 uint256 traversed = _nibblesToTraverse(
                     nodeValue,
                     path,
                     pathPtr
                 );
+                //enforce correct nibble
+                bytes1 prefix = _getNthNibbleOfBytes(0, nodeValue);
                 if (pathPtr + traversed == path.length) {
                     //leaf node
-                    //enforce correct nibble
-                    bytes1 prefix = _getNthNibbleOfBytes(0, nodeValue);
                     if (
                         keccak256(RLPReader.toBytes(currentNodeList[1])) == keccak256(value) && 
                         (prefix == bytes1(uint8(2)) || prefix == bytes1(uint8(3)))
@@ -91,36 +90,12 @@ library MerklePatriciaProof {
                 }
 
                 //extension node
-                if (traversed == 0) {
+                if (traversed == 0 || (prefix != bytes1(uint8(0)) && prefix != bytes1(uint8(1)))) {
                     return false;
                 }
 
                 pathPtr += traversed;
                 nodeKey = bytes32(RLPReader.toUintStrict(currentNodeList[1]));
-                // Alternative 1 end
-
-                // // Alternative 2 start
-                // bytes memory nodeValue = RLPReader.toBytes(currentNodeList[0]);
-                // bytes1 prefix = _getNthNibbleOfBytes(0, nodeValue);
-                // // Extension node
-                // if (prefix == bytes1(uint8(0)) || prefix == bytes1(uint8(1))) {
-                //     uint256 traversed = _nibblesToTraverse(
-                //         nodeValue,
-                //         path,
-                //         pathPtr
-                //     );
-                //     if (traversed == 0) {
-                //         return false;
-                //     }
-                //     pathPtr += traversed; 
-                //     nodeKey = bytes32(RLPReader.toUintStrict(currentNodeList[1]));
-                // // Leaf node
-                // } else if (prefix == bytes1(uint8(2)) || prefix == bytes1(uint8(3))){
-                //     return keccak256(RLPReader.toBytes(currentNodeList[1])) == keccak256(value);
-                // } else {
-                //     return false;
-                // }
-                // // Alternative 2 end
             } else {
                 return false;
             }