diff --git a/pipeline/fiftyone_pipeline_core/src/fiftyone_pipeline_core/flowdata.py b/pipeline/fiftyone_pipeline_core/src/fiftyone_pipeline_core/flowdata.py
index c6f83c7c..914d7596 100644
--- a/pipeline/fiftyone_pipeline_core/src/fiftyone_pipeline_core/flowdata.py
+++ b/pipeline/fiftyone_pipeline_core/src/fiftyone_pipeline_core/flowdata.py
@@ -203,7 +203,8 @@ def set_element_data(self, element_data):
 
         """
 
-        self.data[element_data.flow_element.datakey] = element_data
+        # Kept under the data key in lower case, which is how get reads it.
+        self.data[element_data.flow_element.datakey.lower()] = element_data
 
 
     def set_error(self, flow_error):
diff --git a/pipeline/fiftyone_pipeline_core/src/fiftyone_pipeline_core/jsonbundler.py b/pipeline/fiftyone_pipeline_core/src/fiftyone_pipeline_core/jsonbundler.py
index 9f2a8ca7..4262d740 100644
--- a/pipeline/fiftyone_pipeline_core/src/fiftyone_pipeline_core/jsonbundler.py
+++ b/pipeline/fiftyone_pipeline_core/src/fiftyone_pipeline_core/jsonbundler.py
@@ -103,7 +103,7 @@ def process_internal(self, flowdata):
                         if len(delayed_evidence_properties_list):
                             
                             delayed_evidence_properties[propertykey] = list(map(lambda x:
-                                flow_element.datakey + '.' + x, delayed_evidence_properties_list))
+                                flow_element.datakey.lower() + '.' + x, delayed_evidence_properties_list))
 
 
                 self.property_cache[flow_element.datakey] = {
@@ -115,7 +115,7 @@ def process_internal(self, flowdata):
 
             # Create empty area for FlowElement properties to go
 
-            output[flow_element.datakey] = {}
+            output[flow_element.datakey.lower()] = {}
 
             for propertykey, propertymeta in properties.items():
                 value = None
@@ -125,13 +125,13 @@ def process_internal(self, flowdata):
 
 
                 if propertykey in property_cache["delayExecutionList"]:
-                    output[flow_element.datakey][propertykey.lower() + "delayexecution"] = True
+                    output[flow_element.datakey.lower()][propertykey.lower() + "delayexecution"] = True
                 
 
                 # Check if property has any delayed execution evidence properties and set in JSON if yes
 
                 if propertykey in property_cache["evidenceProperties"]:
-                    output[flow_element.datakey][propertykey.lower() + 'evidenceproperties'] = property_cache["evidenceProperties"][propertykey]
+                    output[flow_element.datakey.lower()][propertykey.lower() + 'evidenceproperties'] = property_cache["evidenceProperties"][propertykey]
                 
 
                 try:
diff --git a/pipeline/fiftyone_pipeline_core/tests/test_jsonbundler_lower_case.py b/pipeline/fiftyone_pipeline_core/tests/test_jsonbundler_lower_case.py
new file mode 100644
index 00000000..028eac4a
--- /dev/null
+++ b/pipeline/fiftyone_pipeline_core/tests/test_jsonbundler_lower_case.py
@@ -0,0 +1,69 @@
+
+"""
+The JSON Builder writes the key of each top-level entry and of each sub-entry,
+including the meta-Property suffixes, in lower case, apart from
+javascriptProperties, as the JSON Builder specification says.
+"""
+
+import unittest
+
+from fiftyone_pipeline_core.aspectproperty_value import AspectPropertyValue
+from fiftyone_pipeline_core.elementdata_dictionary import ElementDataDictionary
+from fiftyone_pipeline_core.flowelement import FlowElement
+from fiftyone_pipeline_core.pipelinebuilder import PipelineBuilder
+
+
+class MixedCaseElement(FlowElement):
+
+    def __init__(self):
+        super(MixedCaseElement, self).__init__()
+        self.datakey = "MixedCase"
+        self.properties = {
+            "DelayedProp": {
+                "name": "DelayedProp", "type": "string",
+                "delayexecution": True},
+            "OtherProp": {
+                "name": "OtherProp", "type": "string",
+                "evidenceproperties": ["delayedprop"]},
+            "EmptyProp": {"name": "EmptyProp", "type": "string"}}
+
+    def process_internal(self, flowdata):
+        # Set as a real element sets it, under its mixed case data key.
+        flowdata.set_element_data(ElementDataDictionary(
+            self, {"DelayedProp": "a", "OtherProp": "b",
+                   "EmptyProp": AspectPropertyValue(
+                       no_value_message="No value")}))
+
+
+class JsonBuilderLowerCaseTests(unittest.TestCase):
+
+    def process(self):
+        pipeline = PipelineBuilder({}).add(MixedCaseElement()).build()
+        self.addCleanup(pipeline.close)
+        flowdata = pipeline.create_flowdata()
+        flowdata.process()
+        return flowdata.jsonbundler.json
+
+    def test_every_key_is_lower_case_but_javascript_properties(self):
+        json = self.process()
+        self.assertIn("javascriptProperties", json)
+        self.assertIn("mixedcase", json)
+        for key, value in json.items():
+            if key == "javascriptProperties":
+                continue
+            self.assertEqual(key.lower(), key)
+            for sub_key in value:
+                self.assertEqual(sub_key.lower(), sub_key, sub_key)
+
+    def test_the_meta_property_keys_are_lower_case(self):
+        section = self.process()["mixedcase"]
+        self.assertTrue(section["delayedpropdelayexecution"])
+        self.assertIn("otherpropevidenceproperties", section)
+        self.assertEqual("No value", section["emptypropnullreason"])
+        self.assertIsNone(section["emptyprop"])
+        self.assertEqual("a", section["delayedprop"])
+        self.assertEqual("b", section["otherprop"])
+
+
+if __name__ == "__main__":
+    unittest.main()