diff --git a/setup.cfg b/setup.cfg
index ba492f5..fee2bf5 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,6 @@
 # coding: utf-8
 [metadata]
-version = 2.4a4
+version = 2.4a5
 name = minijson
 long_description = file: README.md
 long_description_content_type = text/markdown; charset=UTF-8
diff --git a/tests/test_minijson.py b/tests/test_minijson.py
index c9a381b..46e8a4c 100644
--- a/tests/test_minijson.py
+++ b/tests/test_minijson.py
@@ -17,7 +17,15 @@ def assertLoadingIsDecodingError(self, b: bytes):
     def assertSameAfterDumpsAndLoads(self, c):
         self.assertEqual(loads(dumps(c)), c)
 
+    def test_default_returns_nonjsonable(self):
+        """Assert that if transform returns a non-JSONable value, EncodingError is raised"""
+        def transform(c):
+            return c
+
+        self.assertRaises(EncodingError, lambda: dumps(2+3j, transform))
+
     def test_default(self):
+        """Assert the default argument works"""
         def transform(c):
             return c.real, c.imag
 
@@ -25,6 +33,7 @@ def transform(c):
         dumps({'test': 2 + 3j}, transform)
 
     def test_subclasses_of_dicts(self):
+        """Assert that you can correctly serialize subclasses of dict"""
         class Subclass(dict):
             pass
 
@@ -33,6 +42,7 @@ class Subclass(dict):
         self.assertEquals(loads(b), {1: 2, 3: 4})
 
     def test_subclasses_of_lists(self):
+        """Assert that you can correctly serialize subclasses of list"""
         class Subclass(list):
             pass
 
@@ -41,6 +51,7 @@ class Subclass(list):
         self.assertEquals(loads(b), [1, 2, 3])
 
     def test_subclasses_of_tuples(self):
+        """Assert that you can correctly serialize subclasses of tuple"""
         class Subclass(tuple):
             pass
 
@@ -49,6 +60,7 @@ class Subclass(tuple):
         self.assertEquals(loads(b), [1, 2, 3])
 
     def test_malformed(self):
+        """Test unserializing malformed strings yields DecodingError"""
         self.assertRaises(EncodingError, lambda: dumps(2 + 3j))
         self.assertLoadingIsDecodingError(b'\x00\x02a')
         self.assertLoadingIsDecodingError(b'\x00\x02a')