diff --git a/aws_xray_sdk/core/models/entity.py b/aws_xray_sdk/core/models/entity.py
index 293f220b..34378d4a 100644
--- a/aws_xray_sdk/core/models/entity.py
+++ b/aws_xray_sdk/core/models/entity.py
@@ -280,13 +280,16 @@ def to_dict(self):
                         subsegments.append(subsegment.to_dict())
                     entity_dict[key] = subsegments
                 elif key == 'cause':
-                    entity_dict[key] = {}
-                    entity_dict[key]['working_directory'] = self.cause['working_directory']
-                    # exceptions are stored as List
-                    throwables = []
-                    for throwable in value['exceptions']:
-                        throwables.append(throwable.to_dict())
-                    entity_dict[key]['exceptions'] = throwables
+                    if isinstance(self.cause, dict):
+                        entity_dict[key] = {}
+                        entity_dict[key]['working_directory'] = self.cause['working_directory']
+                        # exceptions are stored as List
+                        throwables = []
+                        for throwable in value['exceptions']:
+                            throwables.append(throwable.to_dict())
+                        entity_dict[key]['exceptions'] = throwables
+                    else:
+                        entity_dict[key] = self.cause
                 elif key == 'metadata':
                     entity_dict[key] = metadata_to_dict(value)
                 elif key != 'sampled' and key != ORIGIN_TRACE_HEADER_ATTR_KEY:
diff --git a/tests/test_serialize_entities.py b/tests/test_serialize_entities.py
index da5d50a2..d46d737b 100644
--- a/tests/test_serialize_entities.py
+++ b/tests/test_serialize_entities.py
@@ -260,7 +260,7 @@ class TestException(Exception):
         def __init__(self, message):
             super(TestException, self).__init__(message)
 
-    segment = Segment('test')
+    segment_one = Segment('test')
     
     stack_one = [
         ('/path/to/test.py', 10, 'module', 'another_function()'),
@@ -275,18 +275,18 @@ def __init__(self, message):
     exception_one = TestException('test message one')
     exception_two = TestException('test message two')
 
-    segment.add_exception(exception_one, stack_one, True)
-    segment.add_exception(exception_two, stack_two, False)
+    segment_one.add_exception(exception_one, stack_one, True)
+    segment_one.add_exception(exception_two, stack_two, False)
     
-    segment.close()
+    segment_one.close()
     
-    expected_segment_dict = {
-    "id": segment.id,
+    expected_segment_one_dict = {
+    "id": segment_one.id,
     "name": "test",
-    "start_time": segment.start_time,
+    "start_time": segment_one.start_time,
     "in_progress": False,
     "cause": {
-        "working_directory": segment.cause['working_directory'],
+        "working_directory": segment_one.cause['working_directory'],
         "exceptions": [
             {
                 "id": exception_one._cause_id,
@@ -326,14 +326,39 @@ def __init__(self, message):
             }
         ]
     },
-    "trace_id": segment.trace_id,
+    "trace_id": segment_one.trace_id,
     "fault": True,
-    "end_time": segment.end_time
+    "end_time": segment_one.end_time
     }
 
-    actual_segment_dict = entity_to_dict(segment) 
+    segment_two = Segment('test')
+    subsegment = Subsegment('test', 'local', segment_two)
+
+    subsegment.add_exception(exception_one, stack_one, True)
+    subsegment.add_exception(exception_two, stack_two, False)
+    subsegment.close()
     
-    assert expected_segment_dict == actual_segment_dict
+    # will record cause id instead as same exception already recorded in its subsegment
+    segment_two.add_exception(exception_one, stack_one, True)
+    
+    segment_two.close()
+    
+    expected_segment_two_dict = {
+    "id": segment_two.id,
+    "name": "test",
+    "start_time": segment_two.start_time,
+    "in_progress": False,
+    "cause": exception_one._cause_id,
+    "trace_id": segment_two.trace_id,
+    "fault": True,
+    "end_time": segment_two.end_time
+    }
+
+    actual_segment_one_dict = entity_to_dict(segment_one)
+    actual_segment_two_dict = entity_to_dict(segment_two)
+    
+    assert expected_segment_one_dict == actual_segment_one_dict
+    assert expected_segment_two_dict == actual_segment_two_dict
     
 def test_serialize_subsegment():