diff --git a/tests/hazmat/primitives/test_3des.py b/tests/hazmat/primitives/test_3des.py
index 0197353..586afb4 100644
--- a/tests/hazmat/primitives/test_3des.py
+++ b/tests/hazmat/primitives/test_3des.py
@@ -22,7 +22,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.TripleDES("\x00" * 8), modes.CBC("\x00" * 8)
+        algorithms.TripleDES(b"\x00" * 8), modes.CBC(b"\x00" * 8)
     ),
     skip_message="Does not support TripleDES CBC",
 )
@@ -59,7 +59,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.TripleDES("\x00" * 8), modes.OFB("\x00" * 8)
+        algorithms.TripleDES(b"\x00" * 8), modes.OFB(b"\x00" * 8)
     ),
     skip_message="Does not support TripleDES OFB",
 )
@@ -96,7 +96,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.TripleDES("\x00" * 8), modes.CFB("\x00" * 8)
+        algorithms.TripleDES(b"\x00" * 8), modes.CFB(b"\x00" * 8)
     ),
     skip_message="Does not support TripleDES CFB",
 )
@@ -133,7 +133,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.TripleDES("\x00" * 8), modes.CFB8("\x00" * 8)
+        algorithms.TripleDES(b"\x00" * 8), modes.CFB8(b"\x00" * 8)
     ),
     skip_message="Does not support TripleDES CFB8",
 )
diff --git a/tests/hazmat/primitives/test_aes.py b/tests/hazmat/primitives/test_aes.py
index 2c3e5f9..8826aae 100644
--- a/tests/hazmat/primitives/test_aes.py
+++ b/tests/hazmat/primitives/test_aes.py
@@ -18,7 +18,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.AES("\x00" * 16), modes.CBC("\x00" * 16)
+        algorithms.AES(b"\x00" * 16), modes.CBC(b"\x00" * 16)
     ),
     skip_message="Does not support AES CBC",
 )
@@ -84,7 +84,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.AES("\x00" * 16), modes.OFB("\x00" * 16)
+        algorithms.AES(b"\x00" * 16), modes.OFB(b"\x00" * 16)
     ),
     skip_message="Does not support AES OFB",
 )
@@ -117,7 +117,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.AES("\x00" * 16), modes.CFB("\x00" * 16)
+        algorithms.AES(b"\x00" * 16), modes.CFB(b"\x00" * 16)
     ),
     skip_message="Does not support AES CFB",
 )
@@ -150,7 +150,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.AES("\x00" * 16), modes.CFB8("\x00" * 16)
+        algorithms.AES(b"\x00" * 16), modes.CFB8(b"\x00" * 16)
     ),
     skip_message="Does not support AES CFB8",
 )
@@ -183,7 +183,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.AES("\x00" * 16), modes.CTR("\x00" * 16)
+        algorithms.AES(b"\x00" * 16), modes.CTR(b"\x00" * 16)
     ),
     skip_message="Does not support AES CTR",
 )
@@ -200,7 +200,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.AES("\x00" * 16), modes.GCM("\x00" * 12)
+        algorithms.AES(b"\x00" * 16), modes.GCM(b"\x00" * 12)
     ),
     skip_message="Does not support AES GCM",
 )
diff --git a/tests/hazmat/primitives/test_arc4.py b/tests/hazmat/primitives/test_arc4.py
index 00fc95b..1a17344 100644
--- a/tests/hazmat/primitives/test_arc4.py
+++ b/tests/hazmat/primitives/test_arc4.py
@@ -18,7 +18,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.ARC4("\x00" * 16), None
+        algorithms.ARC4(b"\x00" * 16), None
     ),
     skip_message="Does not support ARC4",
 )
diff --git a/tests/hazmat/primitives/test_block.py b/tests/hazmat/primitives/test_block.py
index 4f7e63b..5d77877 100644
--- a/tests/hazmat/primitives/test_block.py
+++ b/tests/hazmat/primitives/test_block.py
@@ -120,7 +120,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.AES("\x00" * 16), modes.GCM("\x00" * 12)
+        algorithms.AES(b"\x00" * 16), modes.GCM(b"\x00" * 12)
     ),
     skip_message="Does not support AES GCM",
 )
diff --git a/tests/hazmat/primitives/test_blowfish.py b/tests/hazmat/primitives/test_blowfish.py
index de49e86..0c38b98 100644
--- a/tests/hazmat/primitives/test_blowfish.py
+++ b/tests/hazmat/primitives/test_blowfish.py
@@ -18,7 +18,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.Blowfish("\x00" * 56), modes.ECB()
+        algorithms.Blowfish(b"\x00" * 56), modes.ECB()
     ),
     skip_message="Does not support Blowfish ECB",
 )
@@ -35,7 +35,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.Blowfish("\x00" * 56), modes.CBC("\x00" * 8)
+        algorithms.Blowfish(b"\x00" * 56), modes.CBC(b"\x00" * 8)
     ),
     skip_message="Does not support Blowfish CBC",
 )
@@ -52,7 +52,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.Blowfish("\x00" * 56), modes.OFB("\x00" * 8)
+        algorithms.Blowfish(b"\x00" * 56), modes.OFB(b"\x00" * 8)
     ),
     skip_message="Does not support Blowfish OFB",
 )
@@ -69,7 +69,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.Blowfish("\x00" * 56), modes.CFB("\x00" * 8)
+        algorithms.Blowfish(b"\x00" * 56), modes.CFB(b"\x00" * 8)
     ),
     skip_message="Does not support Blowfish CFB",
 )
diff --git a/tests/hazmat/primitives/test_camellia.py b/tests/hazmat/primitives/test_camellia.py
index 8bdcb30..87fcfe3 100644
--- a/tests/hazmat/primitives/test_camellia.py
+++ b/tests/hazmat/primitives/test_camellia.py
@@ -20,7 +20,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.Camellia("\x00" * 16), modes.ECB()
+        algorithms.Camellia(b"\x00" * 16), modes.ECB()
     ),
     skip_message="Does not support Camellia ECB",
 )
@@ -41,7 +41,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.Camellia("\x00" * 16), modes.CBC("\x00" * 16)
+        algorithms.Camellia(b"\x00" * 16), modes.CBC(b"\x00" * 16)
     ),
     skip_message="Does not support Camellia CBC",
 )
@@ -58,7 +58,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.Camellia("\x00" * 16), modes.OFB("\x00" * 16)
+        algorithms.Camellia(b"\x00" * 16), modes.OFB(b"\x00" * 16)
     ),
     skip_message="Does not support Camellia OFB",
 )
@@ -75,7 +75,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.Camellia("\x00" * 16), modes.CFB("\x00" * 16)
+        algorithms.Camellia(b"\x00" * 16), modes.CFB(b"\x00" * 16)
     ),
     skip_message="Does not support Camellia CFB",
 )
diff --git a/tests/hazmat/primitives/test_cast5.py b/tests/hazmat/primitives/test_cast5.py
index 0e4f879..59af84f 100644
--- a/tests/hazmat/primitives/test_cast5.py
+++ b/tests/hazmat/primitives/test_cast5.py
@@ -18,7 +18,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.CAST5("\x00" * 16), modes.ECB()
+        algorithms.CAST5(b"\x00" * 16), modes.ECB()
     ),
     skip_message="Does not support CAST5 ECB",
 )
@@ -35,7 +35,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.CAST5("\x00" * 16), modes.CBC("\x00" * 8)
+        algorithms.CAST5(b"\x00" * 16), modes.CBC(b"\x00" * 8)
     ),
     skip_message="Does not support CAST5 CBC",
 )
@@ -52,7 +52,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.CAST5("\x00" * 16), modes.OFB("\x00" * 8)
+        algorithms.CAST5(b"\x00" * 16), modes.OFB(b"\x00" * 8)
     ),
     skip_message="Does not support CAST5 OFB",
 )
@@ -69,7 +69,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.CAST5("\x00" * 16), modes.CFB("\x00" * 8)
+        algorithms.CAST5(b"\x00" * 16), modes.CFB(b"\x00" * 8)
     ),
     skip_message="Does not support CAST5 CFB",
 )
@@ -86,7 +86,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.CAST5("\x00" * 16), modes.CTR("\x00" * 8)
+        algorithms.CAST5(b"\x00" * 16), modes.CTR(b"\x00" * 8)
     ),
     skip_message="Does not support CAST5 CTR",
 )
diff --git a/tests/hazmat/primitives/test_idea.py b/tests/hazmat/primitives/test_idea.py
index 1b15ed6..75116dc 100644
--- a/tests/hazmat/primitives/test_idea.py
+++ b/tests/hazmat/primitives/test_idea.py
@@ -18,7 +18,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.IDEA("\x00" * 16), modes.ECB()
+        algorithms.IDEA(b"\x00" * 16), modes.ECB()
     ),
     skip_message="Does not support IDEA ECB",
 )
@@ -35,7 +35,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.IDEA("\x00" * 16), modes.CBC("\x00" * 8)
+        algorithms.IDEA(b"\x00" * 16), modes.CBC(b"\x00" * 8)
     ),
     skip_message="Does not support IDEA CBC",
 )
@@ -52,7 +52,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.IDEA("\x00" * 16), modes.OFB("\x00" * 8)
+        algorithms.IDEA(b"\x00" * 16), modes.OFB(b"\x00" * 8)
     ),
     skip_message="Does not support IDEA OFB",
 )
@@ -69,7 +69,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.IDEA("\x00" * 16), modes.CFB("\x00" * 8)
+        algorithms.IDEA(b"\x00" * 16), modes.CFB(b"\x00" * 8)
     ),
     skip_message="Does not support IDEA CFB",
 )
diff --git a/tests/hazmat/primitives/test_keywrap.py b/tests/hazmat/primitives/test_keywrap.py
index f1238c9..f41baed 100644
--- a/tests/hazmat/primitives/test_keywrap.py
+++ b/tests/hazmat/primitives/test_keywrap.py
@@ -29,7 +29,7 @@
     )
     @pytest.mark.supported(
         only_if=lambda backend: backend.cipher_supported(
-            algorithms.AES("\x00" * 16), modes.ECB()
+            algorithms.AES(b"\x00" * 16), modes.ECB()
         ),
         skip_message="Does not support AES key wrap (RFC 3394) because AES-ECB"
                      " is unsupported",
@@ -50,7 +50,7 @@
     )
     @pytest.mark.supported(
         only_if=lambda backend: backend.cipher_supported(
-            algorithms.AES("\x00" * 16), modes.ECB()
+            algorithms.AES(b"\x00" * 16), modes.ECB()
         ),
         skip_message="Does not support AES key wrap (RFC 3394) because AES-ECB"
                      " is unsupported",
@@ -69,7 +69,7 @@
 
     @pytest.mark.supported(
         only_if=lambda backend: backend.cipher_supported(
-            algorithms.AES("\x00" * 16), modes.ECB()
+            algorithms.AES(b"\x00" * 16), modes.ECB()
         ),
         skip_message="Does not support AES key wrap (RFC 3394) because AES-ECB"
                      " is unsupported",
@@ -81,7 +81,7 @@
 
     @pytest.mark.supported(
         only_if=lambda backend: backend.cipher_supported(
-            algorithms.AES("\x00" * 16), modes.ECB()
+            algorithms.AES(b"\x00" * 16), modes.ECB()
         ),
         skip_message="Does not support AES key wrap (RFC 3394) because AES-ECB"
                      " is unsupported",
@@ -92,7 +92,7 @@
 
     @pytest.mark.supported(
         only_if=lambda backend: backend.cipher_supported(
-            algorithms.AES("\x00" * 16), modes.ECB()
+            algorithms.AES(b"\x00" * 16), modes.ECB()
         ),
         skip_message="Does not support AES key wrap (RFC 3394) because AES-ECB"
                      " is unsupported",
diff --git a/tests/hazmat/primitives/test_seed.py b/tests/hazmat/primitives/test_seed.py
index 7697bd8..29cae4f 100644
--- a/tests/hazmat/primitives/test_seed.py
+++ b/tests/hazmat/primitives/test_seed.py
@@ -18,7 +18,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.SEED("\x00" * 16), modes.ECB()
+        algorithms.SEED(b"\x00" * 16), modes.ECB()
     ),
     skip_message="Does not support SEED ECB",
 )
@@ -35,7 +35,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.SEED("\x00" * 16), modes.CBC("\x00" * 16)
+        algorithms.SEED(b"\x00" * 16), modes.CBC(b"\x00" * 16)
     ),
     skip_message="Does not support SEED CBC",
 )
@@ -52,7 +52,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.SEED("\x00" * 16), modes.OFB("\x00" * 16)
+        algorithms.SEED(b"\x00" * 16), modes.OFB(b"\x00" * 16)
     ),
     skip_message="Does not support SEED OFB",
 )
@@ -69,7 +69,7 @@
 
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.SEED("\x00" * 16), modes.CFB("\x00" * 16)
+        algorithms.SEED(b"\x00" * 16), modes.CFB(b"\x00" * 16)
     ),
     skip_message="Does not support SEED CFB",
 )
diff --git a/tests/test_fernet.py b/tests/test_fernet.py
index c272eec..dbce44f 100644
--- a/tests/test_fernet.py
+++ b/tests/test_fernet.py
@@ -45,7 +45,7 @@
 @pytest.mark.requires_backend_interface(interface=HMACBackend)
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
+        algorithms.AES(b"\x00" * 32), modes.CBC(b"\x00" * 16)
     ),
     skip_message="Does not support AES CBC",
 )
@@ -126,7 +126,7 @@
 @pytest.mark.requires_backend_interface(interface=HMACBackend)
 @pytest.mark.supported(
     only_if=lambda backend: backend.cipher_supported(
-        algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
+        algorithms.AES(b"\x00" * 32), modes.CBC(b"\x00" * 16)
     ),
     skip_message="Does not support AES CBC",
 )