diff --git a/CHANGES.rst b/CHANGES.rst
index 4b81a3a..db449aa 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,4 +1,12 @@
 
+Release 1.7.4
+=========================================
+
+* **BUGFIX:** Fixed incorrect ``.to_json()`` serialization of ``null`` values inside of an iterable.
+
+--------------------
+
+
 Release 1.7.3
 =========================================
 
diff --git a/highcharts_core/__version__.py b/highcharts_core/__version__.py
index 6da2111..043606c 100644
--- a/highcharts_core/__version__.py
+++ b/highcharts_core/__version__.py
@@ -1 +1 @@
-__version__ = '1.7.3'
+__version__ = '1.7.4'
diff --git a/highcharts_core/metaclasses.py b/highcharts_core/metaclasses.py
index 0b5d172..cac0c28 100644
--- a/highcharts_core/metaclasses.py
+++ b/highcharts_core/metaclasses.py
@@ -230,7 +230,10 @@ def trim_iterable(untrimmed,
             if checkers.is_type(item, 'CallbackFunction') and to_json:
                 continue
             elif item is None or item == constants.EnforcedNull:
-                trimmed.append('null')
+                if to_json:
+                    trimmed.append(None)
+                else:
+                    trimmed.append('null')
             elif hasattr(item, 'trim_dict'):
                 updated_context = item.__class__.__name__
                 untrimmed_item = item._to_untrimmed_dict()