3 files changed, 4 insertions, 17 deletions
diff --git a/cryptography/hazmat/primitives/ciphers/base.py b/cryptography/hazmat/primitives/ciphers/base.py
index 3d733afc..48e6da6f 100644
--- a/cryptography/hazmat/primitives/ciphers/base.py
+++ b/cryptography/hazmat/primitives/ciphers/base.py
@@ -19,12 +19,7 @@ from cryptography.hazmat.primitives import interfaces
 
 
 class Cipher(object):
-    def __init__(self, algorithm, mode, backend=None):
-        if backend is None:
-            from cryptography.hazmat.bindings import (
-                _default_backend as backend,
-            )
-
+    def __init__(self, algorithm, mode, backend):
         if not isinstance(algorithm, interfaces.CipherAlgorithm):
             raise TypeError("Expected interface of interfaces.CipherAlgorithm")
 
diff --git a/cryptography/hazmat/primitives/hashes.py b/cryptography/hazmat/primitives/hashes.py
index 93fc8c42..bee188b3 100644
--- a/cryptography/hazmat/primitives/hashes.py
+++ b/cryptography/hazmat/primitives/hashes.py
@@ -22,15 +22,11 @@ from cryptography.hazmat.primitives import interfaces
 
 @utils.register_interface(interfaces.HashContext)
 class Hash(object):
-    def __init__(self, algorithm, backend=None, ctx=None):
+    def __init__(self, algorithm, backend, ctx=None):
         if not isinstance(algorithm, interfaces.HashAlgorithm):
             raise TypeError("Expected instance of interfaces.HashAlgorithm.")
         self.algorithm = algorithm
 
-        if backend is None:
-            from cryptography.hazmat.bindings import _default_backend
-            backend = _default_backend
-
         self._backend = backend
 
         if ctx is None:
diff --git a/cryptography/hazmat/primitives/hmac.py b/cryptography/hazmat/primitives/hmac.py
index 08dfae01..2bd8e4d3 100644
--- a/cryptography/hazmat/primitives/hmac.py
+++ b/cryptography/hazmat/primitives/hmac.py
@@ -22,15 +22,11 @@ from cryptography.hazmat.primitives import interfaces
 
 @utils.register_interface(interfaces.HashContext)
 class HMAC(object):
-    def __init__(self, key, algorithm, ctx=None, backend=None):
+    def __init__(self, key, algorithm, backend, ctx=None):
         if not isinstance(algorithm, interfaces.HashAlgorithm):
             raise TypeError("Expected instance of interfaces.HashAlgorithm.")
         self.algorithm = algorithm
 
-        if backend is None:
-            from cryptography.hazmat.bindings import _default_backend
-            backend = _default_backend
-
         self._backend = backend
         self._key = key
         if ctx is None:
@@ -51,7 +47,7 @@ class HMAC(object):
         return HMAC(
             self._key,
             self.algorithm,
-            backend=self._backend,
+            self._backend,
             ctx=self._ctx.copy()
         )