diff --git a/tree.go b/tree.go
index a5f3f57..6f856d0 100644
--- a/tree.go
+++ b/tree.go
@@ -311,13 +311,10 @@ func (t *Tree) AddWithTx(wTx db.WriteTx, k, v []byte) error {
 }
 
 func (t *Tree) add(wTx db.WriteTx, root []byte, fromLvl int, k, v []byte) ([]byte, error) {
-	keyPath := make([]byte, t.hashFunction.Len())
-	// if len(k) > t.hashFunction.Len() { // WIP
-	//         return nil, fmt.Errorf("len(k) > hashFunction.Len()")
-	// }
+	keyPath := make([]byte, int(math.Ceil(float64(t.maxLevels)/float64(8)))) //nolint:gomnd
 	copy(keyPath[:], k)
-
 	path := getPath(t.maxLevels, keyPath)
+
 	// go down to the leaf
 	var siblings [][]byte
 	_, _, siblings, err := t.down(wTx, k, root, siblings, path, fromLvl, false)
@@ -593,12 +590,7 @@ func (t *Tree) UpdateWithTx(wTx db.WriteTx, k, v []byte) error {
 		return ErrSnapshotNotEditable
 	}
 
-	var err error
-
-	keyPath := make([]byte, t.hashFunction.Len())
-	// if len(k) > t.hashFunction.Len() { // WIP
-	//         return fmt.Errorf("len(k) > hashFunction.Len()")
-	// }
+	keyPath := make([]byte, int(math.Ceil(float64(t.maxLevels)/float64(8)))) //nolint:gomnd
 	copy(keyPath[:], k)
 	path := getPath(t.maxLevels, keyPath)
 
@@ -655,18 +647,15 @@ func (t *Tree) GenProof(k []byte) ([]byte, []byte, []byte, bool, error) {
 // GenProofWithTx does the same than the GenProof method, but allowing to pass
 // the db.ReadTx that is used.
 func (t *Tree) GenProofWithTx(rTx db.ReadTx, k []byte) ([]byte, []byte, []byte, bool, error) {
-	keyPath := make([]byte, t.hashFunction.Len())
-	// if len(k) > t.hashFunction.Len() { // WIP
-	//         return nil, nil, nil, false, fmt.Errorf("len(k) > hashFunction.Len()")
-	// }
+	keyPath := make([]byte, int(math.Ceil(float64(t.maxLevels)/float64(8)))) //nolint:gomnd
 	copy(keyPath[:], k)
+	path := getPath(t.maxLevels, keyPath)
 
 	root, err := t.RootWithTx(rTx)
 	if err != nil {
 		return nil, nil, nil, false, err
 	}
 
-	path := getPath(t.maxLevels, keyPath)
 	// go down to the leaf
 	var siblings [][]byte
 	_, value, siblings, err := t.down(rTx, k, root, siblings, path, 0, true)
@@ -793,18 +782,15 @@ func (t *Tree) Get(k []byte) ([]byte, []byte, error) {
 // ErrKeyNotFound, and in the leafK & leafV parameters will be placed the data
 // found in the tree in the leaf that was on the path going to the input key.
 func (t *Tree) GetWithTx(rTx db.ReadTx, k []byte) ([]byte, []byte, error) {
-	keyPath := make([]byte, t.hashFunction.Len())
-	// if len(k) > t.hashFunction.Len() { // WIP
-	//         return nil, nil, fmt.Errorf("len(k) > hashFunction.Len()")
-	// }
+	keyPath := make([]byte, int(math.Ceil(float64(t.maxLevels)/float64(8)))) //nolint:gomnd
 	copy(keyPath[:], k)
+	path := getPath(t.maxLevels, keyPath)
 
 	root, err := t.RootWithTx(rTx)
 	if err != nil {
 		return nil, nil, err
 	}
 
-	path := getPath(t.maxLevels, keyPath)
 	// go down to the leaf
 	var siblings [][]byte
 	_, value, _, err := t.down(rTx, k, root, siblings, path, 0, true)
@@ -827,7 +813,7 @@ func CheckProof(hashFunc HashFunction, k, v, root, packedSiblings []byte) (bool,
 		return false, err
 	}
 
-	keyPath := make([]byte, hashFunc.Len())
+	keyPath := make([]byte, len(siblings))
 	copy(keyPath[:], k)
 
 	key, _, err := newLeafValue(hashFunc, k, v)
diff --git a/tree_test.go b/tree_test.go
index c794377..f6592c4 100644
--- a/tree_test.go
+++ b/tree_test.go
@@ -640,6 +640,40 @@ func TestGetFromSnapshotExpectArboErrKeyNotFound(t *testing.T) {
 	c.Assert(err, qt.Equals, ErrKeyNotFound) // and not equal to db.ErrKeyNotFound
 }
 
+func TestKeyLen(t *testing.T) {
+	c := qt.New(t)
+	database, err := badgerdb.New(badgerdb.Options{Path: c.TempDir()})
+	c.Assert(err, qt.IsNil)
+	// maxLevels is 100, keyPath length = ceil(maxLevels/8) = 13
+	maxLevels := 100
+	tree, err := NewTree(database, maxLevels, HashFunctionPoseidon)
+	c.Assert(err, qt.IsNil)
+
+	// expect no errors when adding a key of only 4 bytes (when the
+	// required length of keyPath for 100 levels would be 13 bytes)
+	bLen := 4
+	k := BigIntToBytes(bLen, big.NewInt(1))
+	v := BigIntToBytes(bLen, big.NewInt(1))
+
+	err = tree.Add(k, v)
+	c.Assert(err, qt.IsNil)
+
+	err = tree.Update(k, v)
+	c.Assert(err, qt.IsNil)
+
+	_, _, _, _, err = tree.GenProof(k)
+	c.Assert(err, qt.IsNil)
+
+	_, _, err = tree.Get(k)
+	c.Assert(err, qt.IsNil)
+
+	k = BigIntToBytes(bLen, big.NewInt(2))
+	v = BigIntToBytes(bLen, big.NewInt(2))
+	invalids, err := tree.AddBatch([][]byte{k}, [][]byte{v})
+	c.Assert(err, qt.IsNil)
+	c.Assert(len(invalids), qt.Equals, 0)
+}
+
 func BenchmarkAdd(b *testing.B) {
 	bLen := 32 // for both Poseidon & Sha256
 	// prepare inputs
diff --git a/vt.go b/vt.go
index 9232ec6..939c6b6 100644
--- a/vt.go
+++ b/vt.go
@@ -44,7 +44,7 @@ func (p *params) keysValuesToKvs(ks, vs [][]byte) ([]kv, error) {
 	}
 	kvs := make([]kv, len(ks))
 	for i := 0; i < len(ks); i++ {
-		keyPath := make([]byte, p.hashFunction.Len())
+		keyPath := make([]byte, int(math.Ceil(float64(p.maxLevels)/float64(8)))) //nolint:gomnd
 		copy(keyPath[:], ks[i])
 		kvs[i].pos = i
 		kvs[i].keyPath = keyPath