diff --git a/src/cryptography/fernet.py b/src/cryptography/fernet.py
index c2e01fc50..a3c9ca61d 100644
--- a/src/cryptography/fernet.py
+++ b/src/cryptography/fernet.py
@@ -30,7 +30,12 @@ class Fernet(object):
         key: typing.Union[bytes, str],
         backend: typing.Any = None,
     ):
-        key = base64.urlsafe_b64decode(key)
+        try:
+            key = base64.urlsafe_b64decode(key)
+        except binascii.Error as exc:
+            raise ValueError(
+                "Fernet key must be 32 url-safe base64-encoded bytes."
+            ) from exc
         if len(key) != 32:
             raise ValueError(
                 "Fernet key must be 32 url-safe base64-encoded bytes."
diff --git a/tests/test_fernet.py b/tests/test_fernet.py
index d3090e04c..5db21f523 100644
--- a/tests/test_fernet.py
+++ b/tests/test_fernet.py
@@ -130,9 +130,10 @@ class TestFernet(object):
         f = Fernet(Fernet.generate_key(), backend=backend)
         assert f.decrypt(f.encrypt(message)) == message
 
-    def test_bad_key(self, backend):
+    @pytest.mark.parametrize("key", [base64.urlsafe_b64encode(b"abc"), b"abc"])
+    def test_bad_key(self, backend, key):
         with pytest.raises(ValueError):
-            Fernet(base64.urlsafe_b64encode(b"abc"), backend=backend)
+            Fernet(key, backend=backend)
 
     def test_extract_timestamp(self, monkeypatch, backend):
         f = Fernet(base64.urlsafe_b64encode(b"\x00" * 32), backend=backend)