diff --git a/src/packerlicious/post_processor.py b/src/packerlicious/post_processor.py
index 613a45a..893b8a2 100644
--- a/src/packerlicious/post_processor.py
+++ b/src/packerlicious/post_processor.py
@@ -320,6 +320,7 @@ class Manifest(PackerPostProcessor):
 
     props = {
         'output': (str, False),
+        'custom_data': (dict, False),
         'strip_path': (validator.boolean, False),
     }
 
diff --git a/tests/packerlicious/test_post_processor_manifest.py b/tests/packerlicious/test_post_processor_manifest.py
index b41152c..086567f 100644
--- a/tests/packerlicious/test_post_processor_manifest.py
+++ b/tests/packerlicious/test_post_processor_manifest.py
@@ -1,4 +1,6 @@
 import packerlicious.post_processor as post_processor
+from packerlicious.template import Template
+import json
 
 
 class TestManifestPostProcessor(object):
@@ -7,3 +9,30 @@ def test_no_required_fields(self):
         b = post_processor.Manifest()
 
         b.to_dict()
+
+    def test_custom_data(self):
+        expected_json = """
+        {
+          "post-processors": [
+            {
+              "type": "manifest",
+              "output": "manifest.json",
+              "strip_path": "true",
+              "custom_data": {
+                "my_custom_data": "example"
+              }
+            }
+          ]
+        }
+        """
+        p = post_processor.Manifest(
+            output="manifest.json",
+            strip_path=True,
+            custom_data={'my_custom_data': 'example'}
+        )
+        t = Template()
+        t.add_post_processor(p)
+
+        to_json = t.to_json()
+        assert to_json == json.dumps(json.loads(expected_json), sort_keys=True, indent=2,
+                                     separators=(',', ': '))