diff --git a/pycardano/key.py b/pycardano/key.py
index 55f9d01f..485ee433 100644
--- a/pycardano/key.py
+++ b/pycardano/key.py
@@ -148,6 +148,9 @@ def __eq__(self, other):
     def __repr__(self) -> str:
         return self.to_json()
 
+    def __hash__(self):
+        return hash(self.payload)
+
 
 class SigningKey(Key):
     def sign(self, data: bytes) -> bytes:
diff --git a/pycardano/txbuilder.py b/pycardano/txbuilder.py
index 14e63adc..fde55e73 100644
--- a/pycardano/txbuilder.py
+++ b/pycardano/txbuilder.py
@@ -1256,7 +1256,7 @@ def build_and_sign(
         witness_set = self.build_witness_set()
         witness_set.vkey_witnesses = []
 
-        for signing_key in signing_keys:
+        for signing_key in set(signing_keys):
             signature = signing_key.sign(tx_body.hash())
             witness_set.vkey_witnesses.append(
                 VerificationKeyWitness(signing_key.to_verification_key(), signature)
diff --git a/test/pycardano/test_key.py b/test/pycardano/test_key.py
index 4f0665ea..3801f246 100644
--- a/test/pycardano/test_key.py
+++ b/test/pycardano/test_key.py
@@ -97,3 +97,18 @@ def test_key_save():
         SK.save(f.name)
         sk = PaymentSigningKey.load(f.name)
         assert SK == sk
+
+
+def test_key_hash():
+    sk = PaymentSigningKey.generate()
+    vk = PaymentVerificationKey.from_signing_key(sk)
+
+    sk_set = set()
+    vk_set = set()
+
+    for _ in range(2):
+        sk_set.add(sk)
+        vk_set.add(vk)
+
+    assert len(sk_set) == 1
+    assert len(vk_set) == 1