pygost/gost3410.py | 2 +-
 pygost/mgm.py      | 8 ++++----
 pygost/wrap.py     | 2 +-

diff --git a/pygost/gost3410.py b/pygost/gost3410.py
index 74c18de549c45b7ca0e641ef74af6966a423996fab17b5719118229ae60f1991..64018323ccc4ba5f25a48b9c01fc47223a7527c0d826c9122fba3a070539388b 100644
--- a/pygost/gost3410.py
+++ b/pygost/gost3410.py
@@ -120,7 +120,7 @@     def st(self):
         """Compute s/t parameters for twisted Edwards curve points conversion
         """
         if self.e is None or self.d is None:
-            raise ValueError("non twisted Edwards curve")
+            raise ValueError("Non twisted Edwards curve")
         if self._st is not None:
             return self._st
         self._st = (
diff --git a/pygost/mgm.py b/pygost/mgm.py
index 452eda4473732cd20c6d1c4ed235b0a89f0285d8b151089007a2d6912dad628a..ed2ca8746aa5e2ee1c45c9d5643b61daca7b79eeb06470acc9817c7cef8ac4e4 100644
--- a/pygost/mgm.py
+++ b/pygost/mgm.py
@@ -57,10 +57,10 @@         :param int tag_size: authentication tag size
                              (defaults to blocksize if not specified)
         """
         if bs not in (8, 16):
-            raise ValueError("only 64/128-bit blocksizes allowed")
+            raise ValueError("Only 64/128-bit blocksizes allowed")
         self.tag_size = bs if tag_size is None else bs
         if self.tag_size < 4 or self.tag_size > bs:
-            raise ValueError("invalid tag_size")
+            raise ValueError("Invalid tag_size")
         self.encrypter = encrypter
         self.bs = bs
         self.max_size = (1 << (bs * 8 // 2)) - 1
@@ -74,7 +74,7 @@             raise ValueError("nonce must not have higher bit set")
 
     def _validate_sizes(self, plaintext, additional_data):
         if len(plaintext) == 0 and len(additional_data) == 0:
-            raise ValueError("at least one of plaintext or additional_data required")
+            raise ValueError("At least one of plaintext or additional_data required")
         if len(plaintext) + len(additional_data) > self.max_size:
             raise ValueError("plaintext+additional_data are too big")
 
@@ -164,5 +164,5 @@             ciphertext[-self.tag_size:],
         )
         tag = self._auth(icn, ciphertext, additional_data)
         if not compare_digest(tag_expected, tag):
-            raise ValueError("invalid authentication tag")
+            raise ValueError("Invalid authentication tag")
         return self._crypt(icn, ciphertext)
diff --git a/pygost/wrap.py b/pygost/wrap.py
index aa307e72c3e91f140ae803a85219e24478d8a1393f00d6094c710a9816b396bf..b10bbee3928a225db95bc91afdcca68b80100ee1e017616232bc99714fd75652 100644
--- a/pygost/wrap.py
+++ b/pygost/wrap.py
@@ -143,5 +143,5 @@     """
     key_and_key_mac = ctr(encrypter_key, bs, kexp, iv)
     key, key_mac = key_and_key_mac[:-bs], key_and_key_mac[-bs:]
     if not compare_digest(mac(encrypter_mac, bs, iv + key), key_mac):
-        raise ValueError("invalid authentication tag")
+        raise ValueError("Invalid authentication tag")
     return key