diff --git a/packages/incremental-merkle-tree.sol/contracts/IncrementalBinaryTree.sol b/packages/incremental-merkle-tree.sol/contracts/IncrementalBinaryTree.sol
index 3b5052e..1e1c867 100644
--- a/packages/incremental-merkle-tree.sol/contracts/IncrementalBinaryTree.sol
+++ b/packages/incremental-merkle-tree.sol/contracts/IncrementalBinaryTree.sol
@@ -71,18 +71,22 @@ library IncrementalBinaryTree {
 
     /// @dev Updates a leaf in the tree.
     /// @param self: Tree data.
-    /// @param leaf: Leaf to be updated.
+    /// @param leaf: [0] = existing leaf to replace, [1] = new leaf to insert
     /// @param proofSiblings: Array of the sibling nodes of the proof of membership.
     /// @param proofPathIndices: Path of the proof of membership.
     function update(
         IncrementalTreeData storage self,
-        uint256 leaf,
+        uint256[2] calldata leaf,
         uint256[] calldata proofSiblings,
         uint8[] calldata proofPathIndices
     ) public {
-        require(leaf < SNARK_SCALAR_FIELD, "IncrementalBinaryTree: leaf must be < SNARK_SCALAR_FIELD");
+        require(
+            verify(self, leaf[0], proofSiblings, proofPathIndices),
+            "IncrementalBinaryTree: provided current leaf not found"
+        );
+        require(leaf[1] < SNARK_SCALAR_FIELD, "IncrementalBinaryTree: leaf must be < SNARK_SCALAR_FIELD");
 
-        uint256 hash = leaf;
+        uint256 hash = leaf[1];
         for (uint8 i = 0; i < self.depth; i++) {
             if (proofPathIndices[i] == 0) {
                 if (proofSiblings[i] == self.lastSubtrees[i][1]) {
diff --git a/packages/incremental-merkle-tree.sol/contracts/IncrementalQuinTree.sol b/packages/incremental-merkle-tree.sol/contracts/IncrementalQuinTree.sol
index 5d9109c..c85a9b8 100644
--- a/packages/incremental-merkle-tree.sol/contracts/IncrementalQuinTree.sol
+++ b/packages/incremental-merkle-tree.sol/contracts/IncrementalQuinTree.sol
@@ -81,18 +81,22 @@ library IncrementalQuinTree {
 
     /// @dev Updates a leaf in the tree.
     /// @param self: Tree data.
-    /// @param leaf: Leaf to be updated.
+    /// @param leaf: [0] = existing leaf to replace, [1] = new leaf to insert
     /// @param proofSiblings: Array of the sibling nodes of the proof of membership.
     /// @param proofPathIndices: Path of the proof of membership.
     function update(
         IncrementalTreeData storage self,
-        uint256 leaf,
+        uint256[2] calldata leaf,
         uint256[4][] calldata proofSiblings,
         uint8[] calldata proofPathIndices
     ) public {
-        require(leaf < SNARK_SCALAR_FIELD, "IncrementalQuinTree: leaf must be < SNARK_SCALAR_FIELD");
+        require(
+            verify(self, leaf[0], proofSiblings, proofPathIndices),
+            "IncrementalQuinTree: provided current leaf not found"
+        );
+        require(leaf[1] < SNARK_SCALAR_FIELD, "IncrementalQuinTree: leaf must be < SNARK_SCALAR_FIELD");
 
-        uint256 hash = leaf;
+        uint256 hash = leaf[1];
 
         for (uint8 i = 0; i < self.depth; i++) {
             uint256[5] memory nodes;
diff --git a/packages/incremental-merkle-tree.sol/contracts/test/IncrementalBinaryTreeTest.sol b/packages/incremental-merkle-tree.sol/contracts/test/IncrementalBinaryTreeTest.sol
index 85e54b6..d3c12d6 100644
--- a/packages/incremental-merkle-tree.sol/contracts/test/IncrementalBinaryTreeTest.sol
+++ b/packages/incremental-merkle-tree.sol/contracts/test/IncrementalBinaryTreeTest.sol
@@ -32,7 +32,7 @@ contract IncrementalBinaryTreeTest {
 
     function updateLeaf(
         bytes32 _treeId,
-        uint256 _leaf,
+        uint256[2] calldata _leaf,
         uint256[] calldata _proofSiblings,
         uint8[] calldata _proofPathIndices
     ) external {
@@ -40,7 +40,7 @@ contract IncrementalBinaryTreeTest {
 
         trees[_treeId].update(_leaf, _proofSiblings, _proofPathIndices);
 
-        emit LeafUpdated(_treeId, _leaf, trees[_treeId].root);
+        emit LeafUpdated(_treeId, _leaf[1], trees[_treeId].root);
     }
 
     function removeLeaf(
diff --git a/packages/incremental-merkle-tree.sol/contracts/test/IncrementalQuinTreeTest.sol b/packages/incremental-merkle-tree.sol/contracts/test/IncrementalQuinTreeTest.sol
index 090af54..1cf1dfc 100644
--- a/packages/incremental-merkle-tree.sol/contracts/test/IncrementalQuinTreeTest.sol
+++ b/packages/incremental-merkle-tree.sol/contracts/test/IncrementalQuinTreeTest.sol
@@ -32,7 +32,7 @@ contract IncrementalQuinTreeTest {
 
     function updateLeaf(
         bytes32 _treeId,
-        uint256 _leaf,
+        uint256[2] calldata _leaf,
         uint256[4][] calldata _proofSiblings,
         uint8[] calldata _proofPathIndices
     ) external {
@@ -40,7 +40,7 @@ contract IncrementalQuinTreeTest {
 
         trees[_treeId].update(_leaf, _proofSiblings, _proofPathIndices);
 
-        emit LeafUpdated(_treeId, _leaf, trees[_treeId].root);
+        emit LeafUpdated(_treeId, _leaf[1], trees[_treeId].root);
     }
 
     function removeLeaf(
diff --git a/packages/incremental-merkle-tree.sol/test/IncrementalBinaryTreeTest.ts b/packages/incremental-merkle-tree.sol/test/IncrementalBinaryTreeTest.ts
index b0ad131..0c2072f 100644
--- a/packages/incremental-merkle-tree.sol/test/IncrementalBinaryTreeTest.ts
+++ b/packages/incremental-merkle-tree.sol/test/IncrementalBinaryTreeTest.ts
@@ -86,7 +86,7 @@ describe("IncrementalBinaryTreeTest", () => {
     it("Should not update a leaf if the tree does not exist", async () => {
         const treeId = ethers.utils.formatBytes32String("none")
 
-        const transaction = contract.updateLeaf(treeId, leaf, [0, 1], [0, 1])
+        const transaction = contract.updateLeaf(treeId, [leaf, leaf], [0, 1], [0, 1])
 
         await expect(transaction).to.be.revertedWith("BinaryTreeTest: tree does not exist")
     })
@@ -94,11 +94,29 @@ describe("IncrementalBinaryTreeTest", () => {
     it("Should not update a leaf if its value is > SNARK_SCALAR_FIELD", async () => {
         const leaf = BigInt("21888242871839275222246405745257275088548364400416034343698204186575808495618")
 
-        const transaction = contract.updateLeaf(treeId, leaf, [0, 1], [0, 1])
+        const transaction = contract.updateLeaf(treeId, [leaf, leaf], [0, 1], [0, 1])
 
         await expect(transaction).to.be.revertedWith("IncrementalBinaryTree: leaf must be < SNARK_SCALAR_FIELD")
     })
 
+    it("Should not update a leaf if wrong current leaf is given", async () => {
+        const treeId = ethers.utils.formatBytes32String("tree2")
+        const tree = createTree(depth, 0)
+        for (let i = 0; i < 4; i += 1) tree.insert(BigInt(i + 1))
+
+        const leaf = BigInt(1337)
+        tree.update(2, leaf)
+        const { pathIndices, siblings } = tree.createProof(2)
+        const transaction = contract.updateLeaf(
+            treeId,
+            [leaf, leaf],
+            siblings.map((s) => s[0]),
+            pathIndices
+        )
+
+        await expect(transaction).to.be.revertedWith("IncrementalBinaryTree: provided current leaf not found")
+    })
+
     it("Should update a leaf", async () => {
         const treeId = ethers.utils.formatBytes32String("tree2")
         const tree = createTree(depth, 0)
@@ -109,7 +127,7 @@ describe("IncrementalBinaryTreeTest", () => {
         const { root, pathIndices, siblings } = tree.createProof(2)
         const transaction = contract.updateLeaf(
             treeId,
-            leaf,
+            [BigInt(3), leaf],
             siblings.map((s) => s[0]),
             pathIndices
         )
diff --git a/packages/incremental-merkle-tree.sol/test/IncrementalQuinTreeTest.ts b/packages/incremental-merkle-tree.sol/test/IncrementalQuinTreeTest.ts
index 97bb78c..74dcede 100644
--- a/packages/incremental-merkle-tree.sol/test/IncrementalQuinTreeTest.ts
+++ b/packages/incremental-merkle-tree.sol/test/IncrementalQuinTreeTest.ts
@@ -89,7 +89,7 @@ describe("IncrementalQuinTreeTest", () => {
     it("Should not update a leaf if the tree does not exist", async () => {
         const treeId = ethers.utils.formatBytes32String("none")
 
-        const transaction = contract.updateLeaf(treeId, leaf, [[0, 1, 2, 3]], [0])
+        const transaction = contract.updateLeaf(treeId, [leaf, leaf], [[0, 1, 2, 3]], [0])
 
         await expect(transaction).to.be.revertedWith("QuinTreeTest: tree does not exist")
     })
@@ -97,11 +97,24 @@ describe("IncrementalQuinTreeTest", () => {
     it("Should not update a leaf if its value is > SNARK_SCALAR_FIELD", async () => {
         const leaf = BigInt("21888242871839275222246405745257275088548364400416034343698204186575808495618")
 
-        const transaction = contract.updateLeaf(treeId, leaf, [[0, 1, 2, 3]], [0])
+        const transaction = contract.updateLeaf(treeId, [leaf, leaf], [[0, 1, 2, 3]], [0])
 
         await expect(transaction).to.be.revertedWith("IncrementalQuinTree: leaf must be < SNARK_SCALAR_FIELD")
     })
 
+    it("Should not update a leaf if wrong current leaf is given", async () => {
+        const treeId = ethers.utils.formatBytes32String("tree2")
+        const tree = createTree(depth, 0, 5)
+        for (let i = 0; i < 6; i += 1) tree.insert(BigInt(i + 1))
+
+        const leaf = BigInt(1337)
+        tree.update(2, leaf)
+        const { pathIndices, siblings } = tree.createProof(2)
+        const transaction = contract.updateLeaf(treeId, [leaf, leaf], siblings, pathIndices)
+
+        await expect(transaction).to.be.revertedWith("IncrementalQuinTree: provided current leaf not found")
+    })
+
     it("Should update a leaf", async () => {
         const treeId = ethers.utils.formatBytes32String("tree2")
         const tree = createTree(depth, 0, 5)
@@ -110,7 +123,7 @@ describe("IncrementalQuinTreeTest", () => {
         const leaf = BigInt(1337)
         tree.update(2, leaf)
         const { pathIndices, siblings, root } = tree.createProof(2)
-        const transaction = contract.updateLeaf(treeId, leaf, siblings, pathIndices)
+        const transaction = contract.updateLeaf(treeId, [BigInt(3), leaf], siblings, pathIndices)
 
         await expect(transaction).to.emit(contract, "LeafUpdated").withArgs(treeId, leaf, root)
     })