diff --git a/src/cryptography/exceptions.py b/src/cryptography/exceptions.py
index a4292eb..29be22b 100644
--- a/src/cryptography/exceptions.py
+++ b/src/cryptography/exceptions.py
@@ -49,7 +49,9 @@
 
 
 class InternalError(Exception):
-    pass
+    def __init__(self, msg, err_code):
+        super(InternalError, self).__init__(msg)
+        self.err_code = err_code
 
 
 class InvalidKey(Exception):
diff --git a/src/cryptography/hazmat/backends/commoncrypto/backend.py b/src/cryptography/hazmat/backends/commoncrypto/backend.py
index 091fbb7..315d67d 100644
--- a/src/cryptography/hazmat/backends/commoncrypto/backend.py
+++ b/src/cryptography/hazmat/backends/commoncrypto/backend.py
@@ -227,7 +227,8 @@
         else:
             raise InternalError(
                 "The backend returned an unknown error, consider filing a bug."
-                " Code: {0}.".format(response)
+                " Code: {0}.".format(response),
+                response
             )
 
     def _release_cipher_ctx(self, ctx):
diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index a8f639d..89b1a7b 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -738,22 +738,9 @@
 
         return self._ffi.buffer(buf)[:]
 
-    def _err_string(self, code):
-        err_buf = self._ffi.new("char[]", 256)
-        self._lib.ERR_error_string_n(code, err_buf, 256)
-        return self._ffi.string(err_buf, 256)[:]
-
     def _consume_errors(self):
         return binding._consume_errors(self._lib)
 
-    def _unknown_error(self, error):
-        return InternalError(
-            "Unknown error code {0} from OpenSSL, "
-            "you should probably file a bug. {1}.".format(
-                error.code, self._err_string(error.code)
-            )
-        )
-
     def _bn_to_int(self, bn):
         assert bn != self._ffi.NULL
         if six.PY3:
diff --git a/src/cryptography/hazmat/backends/openssl/ciphers.py b/src/cryptography/hazmat/backends/openssl/ciphers.py
index 4c1c7bc..a80708a 100644
--- a/src/cryptography/hazmat/backends/openssl/ciphers.py
+++ b/src/cryptography/hazmat/backends/openssl/ciphers.py
@@ -136,23 +136,21 @@
             if not errors and isinstance(self._mode, modes.GCM):
                 raise InvalidTag
 
-            assert errors
-
-            if errors[0][1:] == (
-                self._backend._lib.ERR_LIB_EVP,
-                self._backend._lib.EVP_F_EVP_ENCRYPTFINAL_EX,
-                self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH
-            ) or errors[0][1:] == (
-                self._backend._lib.ERR_LIB_EVP,
-                self._backend._lib.EVP_F_EVP_DECRYPTFINAL_EX,
-                self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH
-            ):
-                raise ValueError(
-                    "The length of the provided data is not a multiple of "
-                    "the block length."
+            self._backend.openssl_assert(
+                errors[0][1:] == (
+                    self._backend._lib.ERR_LIB_EVP,
+                    self._backend._lib.EVP_F_EVP_ENCRYPTFINAL_EX,
+                    self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH
+                ) or errors[0][1:] == (
+                    self._backend._lib.ERR_LIB_EVP,
+                    self._backend._lib.EVP_F_EVP_DECRYPTFINAL_EX,
+                    self._backend._lib.EVP_R_DATA_NOT_MULTIPLE_OF_BLOCK_LENGTH
                 )
-            else:
-                raise self._backend._unknown_error(errors[0])
+            )
+            raise ValueError(
+                "The length of the provided data is not a multiple of "
+                "the block length."
+            )
 
         if (isinstance(self._mode, modes.GCM) and
            self._operation == self._ENCRYPT):
diff --git a/src/cryptography/hazmat/bindings/commoncrypto/binding.py b/src/cryptography/hazmat/bindings/commoncrypto/binding.py
index 1695c04..dfe046b 100644
--- a/src/cryptography/hazmat/bindings/commoncrypto/binding.py
+++ b/src/cryptography/hazmat/bindings/commoncrypto/binding.py
@@ -13,6 +13,3 @@
     """
     lib = lib
     ffi = ffi
-
-    def __init__(self):
-        pass
diff --git a/src/cryptography/hazmat/bindings/openssl/binding.py b/src/cryptography/hazmat/bindings/openssl/binding.py
index a5635f7..47b1d6e 100644
--- a/src/cryptography/hazmat/bindings/openssl/binding.py
+++ b/src/cryptography/hazmat/bindings/openssl/binding.py
@@ -9,6 +9,7 @@
 import threading
 import types
 
+from cryptography.exceptions import InternalError
 from cryptography.hazmat.bindings._openssl import ffi, lib
 from cryptography.hazmat.bindings.openssl._conditional import CONDITIONAL_NAMES
 
@@ -17,12 +18,6 @@
                                        ["code", "lib", "func", "reason"])
 
 
-class UnhandledOpenSSLError(Exception):
-    def __init__(self, msg, errors):
-        super(UnhandledOpenSSLError, self).__init__(msg)
-        self.errors = errors
-
-
 def _consume_errors(lib):
     errors = []
     while True:
@@ -41,7 +36,7 @@
 def _openssl_assert(lib, ok):
     if not ok:
         errors = _consume_errors(lib)
-        raise UnhandledOpenSSLError(
+        raise InternalError(
             "Unknown OpenSSL error. Please file an issue at https://github.com"
             "/pyca/cryptography/issues with information on how to reproduce "
             "this.",
diff --git a/tests/hazmat/backends/test_openssl.py b/tests/hazmat/backends/test_openssl.py
index abd707c..8fd0d71 100644
--- a/tests/hazmat/backends/test_openssl.py
+++ b/tests/hazmat/backends/test_openssl.py
@@ -20,7 +20,6 @@
     Backend, backend
 )
 from cryptography.hazmat.backends.openssl.ec import _sn_to_elliptic_curve
-from cryptography.hazmat.bindings.openssl.binding import UnhandledOpenSSLError
 from cryptography.hazmat.primitives import hashes, serialization
 from cryptography.hazmat.primitives.asymmetric import dsa, ec, padding
 from cryptography.hazmat.primitives.ciphers import (
@@ -125,7 +124,7 @@
 
     def test_openssl_assert(self):
         backend.openssl_assert(True)
-        with pytest.raises(UnhandledOpenSSLError):
+        with pytest.raises(InternalError):
             backend.openssl_assert(False)
 
     def test_consume_errors(self):
@@ -140,23 +139,6 @@
         assert backend._lib.ERR_peek_error() == 0
         assert len(errors) == 10
 
-    def test_openssl_error_string(self):
-        backend._lib.ERR_put_error(
-            backend._lib.ERR_LIB_EVP,
-            backend._lib.EVP_F_EVP_DECRYPTFINAL_EX,
-            0,
-            b"test_openssl.py",
-            -1
-        )
-
-        errors = backend._consume_errors()
-        exc = backend._unknown_error(errors[0])
-
-        assert (
-            "digital envelope routines:"
-            "EVP_DecryptFinal_ex:digital envelope routines" in str(exc)
-        )
-
     def test_ssl_ciphers_registered(self):
         meth = backend._lib.TLSv1_method()
         ctx = backend._lib.SSL_CTX_new(meth)