diff --git a/acme/jose/interfaces_test.py b/acme/jose/interfaces_test.py
index 1fd1d3362..380c3a2a5 100644
--- a/acme/jose/interfaces_test.py
+++ b/acme/jose/interfaces_test.py
@@ -44,8 +44,7 @@ class JSONDeSerializableTest(unittest.TestCase):
 
             @classmethod
             def from_json(cls, jobj):
-                return cls(Basic.from_json(jobj.keys()[0]),
-                           Basic.from_json(jobj.values()[0]))
+                pass  # pragma: no cover
 
         self.basic1 = Basic('foo1')
         self.basic2 = Basic('foo2')
diff --git a/acme/jose/json_util_test.py b/acme/jose/json_util_test.py
index aed95e070..5726ef2a8 100644
--- a/acme/jose/json_util_test.py
+++ b/acme/jose/json_util_test.py
@@ -45,10 +45,10 @@ class FieldTest(unittest.TestCase):
         class MockField(interfaces.JSONDeSerializable):
             # pylint: disable=missing-docstring
             def to_partial_json(self):
-                return 'foo'
+                return 'foo'  # pragma: no cover
             @classmethod
             def from_json(cls, jobj):
-                pass
+                pass  # pragma: no cover
         mock_field = MockField()
 
         from acme.jose.json_util import Field
diff --git a/acme/jose/jwa_test.py b/acme/jose/jwa_test.py
index d8b5361b8..f66b2a250 100644
--- a/acme/jose/jwa_test.py
+++ b/acme/jose/jwa_test.py
@@ -26,10 +26,10 @@ class JWASignatureTest(unittest.TestCase):
             # pylint: disable=missing-docstring,too-few-public-methods
             # pylint: disable=abstract-class-not-used
             def sign(self, key, msg):
-                raise NotImplementedError()
+                raise NotImplementedError()  # pragma: no cover
 
             def verify(self, key, msg, sig):
-                raise NotImplementedError()
+                raise NotImplementedError()  # pragma: no cover
 
         # pylint: disable=invalid-name
         self.Sig1 = MockSig('Sig1')
diff --git a/tox.cover.sh b/tox.cover.sh
index d707e00ec..521d73883 100755
--- a/tox.cover.sh
+++ b/tox.cover.sh
@@ -18,5 +18,5 @@ cover () {
 # don't use sequential composition (;), if letsencrypt_nginx returns
 # 0, coveralls submit will be triggered (c.f. .travis.yml,
 # after_success)
-cover letsencrypt 94 && cover acme 99 && \
+cover letsencrypt 94 && cover acme 100 && \
     cover letsencrypt_apache 78 && cover letsencrypt_nginx 94