diff --git a/merkletools/__init__.py b/merkletools/__init__.py
index 2060723..c0d9c95 100644
--- a/merkletools/__init__.py
+++ b/merkletools/__init__.py
@@ -1,21 +1,10 @@
 import hashlib
 import binascii
-try:
-    import sha3
-except:
-    from warnings import warn
-    warn("sha3 is not working!")
 
 
 class MerkleTools(object):
-    def __init__(self, hash_type="sha256"):
-        hash_type = hash_type.lower()
-        if hash_type in ['sha256', 'md5', 'sha224', 'sha384', 'sha512',
-                         'sha3_256', 'sha3_224', 'sha3_384', 'sha3_512']:
-            self.hash_function = getattr(hashlib, hash_type)
-        else:
-            raise Exception('`hash_type` {} nor supported'.format(hash_type))
-
+    def __init__(self, hash_function=hashlib.sha256):
+        self.hash_function = hash_function
         self.reset_tree()
 
     def _to_hex(self, x):
diff --git a/tests/test_merkle_tools.py b/tests/test_merkle_tools.py
index 89089ca..91c1033 100644
--- a/tests/test_merkle_tools.py
+++ b/tests/test_merkle_tools.py
@@ -1,4 +1,5 @@
 import hashlib
+import sha3
 from math import sqrt
 from merkletools import MerkleTools
 
@@ -100,7 +101,7 @@ def test_md5_tree():
     bRightmd5 = '92eb5ffee6ae2fec3ad71c777531578f'
     mRootmd5 = hashlib.md5(bytearray.fromhex(bLeftmd5)+bytearray.fromhex(bRightmd5)).hexdigest()
 
-    mt = MerkleTools('md5')
+    mt = MerkleTools(hash_function=hashlib.md5)
     mt.add_leaf([bLeftmd5, bRightmd5])
     mt.make_tree()
     assert mt.get_merkle_root() == mRootmd5
@@ -169,7 +170,7 @@ def test_validate_5_leaves():
 
 # testing other hash functions
 def test_sha224():
-    mt = MerkleTools(hash_type='sha224')
+    mt = MerkleTools(hash_function=hashlib.sha224)
     mt.add_leaf([
         '90a3ed9e32b2aaf4c61c410eb925426119e1a9dc53d4286ade99a809',
         '35f757ad7f998eb6dd3dd1cd3b5c6de97348b84a951f13de25355177'
@@ -182,7 +183,7 @@ def test_sha224():
 
 
 def test_sha256():
-    mt = MerkleTools(hash_type='sha256')
+    mt = MerkleTools(hash_function=hashlib.sha256)
     mt.add_leaf([
         '1516f000de6cff5c8c63eef081ebcec2ad2fdcf7034db16045d024a90341e07d',
         'e20af19f85f265579ead2578859bf089c92b76a048606983ad83f27ba8f32f1a'
@@ -195,7 +196,7 @@ def test_sha256():
 
 
 def test_sha384():
-    mt = MerkleTools(hash_type='sha384')
+    mt = MerkleTools(hash_function=hashlib.sha384)
     mt.add_leaf([
         '84ae8c6367d64899aef44a951edfa4833378b9e213f916c5eb8492cc37cb951c726e334dace7dbe4bb1dc80c1efe33d0',
         '368c89a00446010def75ad7b179cea9a3d24f8cbb7e2755a28638d194809e7b614eb45453665032860b6c1a135fb6e8b'
@@ -208,7 +209,7 @@ def test_sha384():
 
 
 def test_sha512():
-    mt = MerkleTools(hash_type='sha512')
+    mt = MerkleTools(hash_function=hashlib.sha512)
     mt.add_leaf([
         'c0a8907588c1da716ce31cbef05da1a65986ec23afb75cd42327634dd53d754be6c00a22d6862a42be5f51187a8dff695c530a797f7704e4eb4b473a14ab416e',
         'df1e07eccb2a2d4e1b30d11e646ba13ddc426c1aefbefcff3639405762f216fdcc40a684f3d1855e6d465f99fd9547e53fa8a485f18649fedec5448b45963976'
@@ -221,7 +222,7 @@ def test_sha512():
 
 
 def test_sha3_224():
-    mt = MerkleTools(hash_type='sha3_224')
+    mt = MerkleTools(hash_function=hashlib.sha3_224)
     mt.add_leaf([
         '6ed712b9472b671fd70bb950dc4ccfce197c92a7969f6bc2aa6b6d9f',
         '08db5633d406804d044a3e67683e179b5ee51249ed2139c239d1e65a'
@@ -234,7 +235,7 @@ def test_sha3_224():
 
 
 def test_sha3_224():
-    mt = MerkleTools(hash_type='sha3_224')
+    mt = MerkleTools(hash_function=hashlib.sha3_224)
     mt.add_leaf([
         '6ed712b9472b671fd70bb950dc4ccfce197c92a7969f6bc2aa6b6d9f',
         '08db5633d406804d044a3e67683e179b5ee51249ed2139c239d1e65a'
@@ -247,7 +248,7 @@ def test_sha3_224():
 
 
 def test_sha3_256():
-    mt = MerkleTools(hash_type='sha3_256')
+    mt = MerkleTools(hash_function=hashlib.sha3_256)
     mt.add_leaf([
         '1d7d4ea1cc029ca460e486642830c284657ea0921235c46298b51f0ed1bb7bf7',
         '89b9e14eae37e999b096a6f604adefe7feea4dc240ccecb5e4e92785cffc7070'
@@ -260,7 +261,7 @@ def test_sha3_256():
 
 
 def test_sha3_384():
-    mt = MerkleTools(hash_type='sha3_384')
+    mt = MerkleTools(hash_function=hashlib.sha3_384)
     mt.add_leaf([
         'e222605f939aa69b964a0a03d7075676bb3dbb40c3bd10b22f0adcb149434e7c1085c206f0e3371470a49817aa6d5b16',
         'ae331b6f8643ed7e404471c81be9a74f73fc84ffd5140a0ec9aa8596fa0d0a2ded5f7b780bb2fbfc4e2226ee2a04a2fa'
@@ -273,7 +274,7 @@ def test_sha3_384():
 
 
 def test_sha3_512():
-    mt = MerkleTools(hash_type='sha3_512')
+    mt = MerkleTools(hash_function=hashlib.sha3_512)
     mt.add_leaf([
         '004a237ea808cd9375ee9db9f85625948a890c54e2c30f736f54c969074eb56f0ff3d43dafb4b40d5d974acc1c2a68c046fa4d7c2c20cab6df956514040d0b8b',
         '0b43a85d08c05252d0e23c96bc6b1bda11dfa787049ff452b3c86f4c6135e870c058c05131f199ef8619cfac937a736bbc936a667e4d96a5bf68e4056ce5fdce'