diff --git a/test/integration/test_session.py b/test/integration/test_session.py
index 14b1ad73f..e17fca0f6 100644
--- a/test/integration/test_session.py
+++ b/test/integration/test_session.py
@@ -17,7 +17,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 from unittest import SkipTest
 from uuid import uuid4
 
@@ -434,7 +433,21 @@ def test_should_sync_after_rollback(self):
             assert len(buffer) == 1
             assert buffer[0][0] == 1
 
-    def test_errors_on_run(self):
+    def test_errors_on_write_transaction(self):
+        session = self.driver.session()
+        with self.assertRaises(TypeError):
+            session.write_transaction(lambda tx, uuid : tx.run("CREATE (a:Thing {uuid:$uuid})", uuid=uuid), uuid4())
+        session.close()
+
+    def test_errors_on_run_transaction(self):
+        session = self.driver.session()
+        tx = session.begin_transaction()
+        with self.assertRaises(TypeError):
+            tx.run("CREATE (a:Thing {uuid:$uuid})", uuid=uuid4())
+        tx.rollback()
+        session.close()
+
+    def test_errors_on_run_session(self):
         session = self.driver.session()
         session.close()
         with self.assertRaises(SessionError):
diff --git a/test/unit/test_packstream.py b/test/unit/test_packstream.py
index 33f733cc7..f6ad601bb 100644
--- a/test/unit/test_packstream.py
+++ b/test/unit/test_packstream.py
@@ -24,6 +24,7 @@
 from io import BytesIO
 from math import pi
 from unittest import TestCase
+from uuid import uuid4
 
 from neo4j.bolt.io import MessageFrame as PyMessageFrame
 from neo4j.packstream.packer import Packer as PyPacker
@@ -273,12 +274,8 @@ def test_map_stream(self):
                                  (unpacked, unpacked_value))
 
     def test_illegal_signature(self):
-        try:
+        with self.assertRaises(ValueError):
             self.assert_packable((b"XXX", ()), b"\xB0XXX")
-        except ValueError:
-            assert True
-        else:
-            assert False
 
     def test_empty_struct(self):
         self.assert_packable((b"X", ()), b"\xB0X")
@@ -286,6 +283,9 @@ def test_empty_struct(self):
     def test_tiny_struct(self):
         self.assert_packable((b"Z", (u"A", 1)), b"\xB2Z\x81A\x01")
 
+    def test_illegal_uuid(self):
+        with self.assertRaises(ValueError):
+            self.assert_packable(uuid4(), b"\xB0XXX")
 
 try:
     from neo4j.bolt._io import MessageFrame as CMessageFrame