diff --git a/solidity/contracts/BTCUtils.sol b/solidity/contracts/BTCUtils.sol
index c4e74e1a..975edfb3 100644
--- a/solidity/contracts/BTCUtils.sol
+++ b/solidity/contracts/BTCUtils.sol
@@ -802,7 +802,11 @@ library BTCUtils {
         // i moves in increments of 32
         for (uint i = 0; i < _tree.length; i += 32) {
             if (_idx % 2 == 1) {
-                _current = _hash256MerkleStep(_tree.slice32(i), _current);
+                bytes32 _left = _tree.slice32(i);
+                if (_left == _current) {
+                    return false;
+                }
+                _current = _hash256MerkleStep(_left, _current);
             } else {
                 _current = _hash256MerkleStep(_current, _tree.slice32(i));
             }
diff --git a/testVectors.json b/testVectors.json
index a1d3bc7f..b816ffcc 100644
--- a/testVectors.json
+++ b/testVectors.json
@@ -888,6 +888,20 @@
         "index": 0
       },
       "output": false
+    },
+    {
+      "input": {
+        "proof": "0x0D02210B9177CFC8193B95254473FF7BD986ED1179C276D12BAD5BDBA2403AD40D02210B9177CFC8193B95254473FF7BD986ED1179C276D12BAD5BDBA2403AD4D467A41E18243ABAB48B946D4E235092F87C3F1E1E2B87BC06D3BE1F29E13DCEF94B61259C7E9AF3455B277275800D0D6A58B929EEDF9E0153A6EF2278A5D534",
+        "index": 2
+      },
+      "output": true
+    },
+    {
+      "input": {
+        "proof": "0x0D02210B9177CFC8193B95254473FF7BD986ED1179C276D12BAD5BDBA2403AD40D02210B9177CFC8193B95254473FF7BD986ED1179C276D12BAD5BDBA2403AD4D467A41E18243ABAB48B946D4E235092F87C3F1E1E2B87BC06D3BE1F29E13DCEF94B61259C7E9AF3455B277275800D0D6A58B929EEDF9E0153A6EF2278A5D534",
+        "index": 3
+      },
+      "output": false
     }
   ],
   "getErrBadLength": [