diff --git a/sapling_merkle_tree.py b/sapling_merkle_tree.py
index d6ad35b..86172fc 100644
--- a/sapling_merkle_tree.py
+++ b/sapling_merkle_tree.py
@@ -1,9 +1,24 @@
 #!/usr/bin/env python3
+from binascii import unhexlify
+
 from sapling_pedersen import pedersen_hash
-from sapling_utils import i2lebsp
+from sapling_utils import i2lebsp, leos2bsp
 
 MERKLE_DEPTH = 32
 
 def merkle_crh(layer, left, right):
-    l = i2lebsp(6, MERKLE_DEPTH - 1 - layer)
+    assert layer < MERKLE_DEPTH
+    assert len(left) == 255
+    assert len(right) == 255
+    l = i2lebsp(6, layer)
     return pedersen_hash(b'Zcash_PH', l + left + right)
+
+
+a = unhexlify('87a086ae7d2252d58729b30263fb7b66308bf94ef59a76c9c86e7ea016536505')[::-1]
+b = unhexlify('a75b84a125b2353da7e8d96ee2a15efe4de23df9601b9d9564ba59de57130406')[::-1]
+c = unhexlify('5bf43b5736c19b714d1f462c9d22ba3492c36e3d9bbd7ca24d94b440550aa561')[::-1]
+a = leos2bsp(a)[:255]
+b = leos2bsp(b)[:255]
+c = leos2bsp(c)[:255]
+assert merkle_crh(25, a, b) == c
+assert merkle_crh(26, a, b) != c