diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index c1fbb10..08928d2 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -29,6 +29,8 @@ jobs:
       - run: pipenv run coverage run -m pytest tests/ -svv
       - name: upload coverage to coveralls
         uses: coverallsapp/github-action@v2
+        with:
+          fail-on-error: false
 
   sam-build-and-lint:
     runs-on: ubuntu-latest
diff --git a/set_tags/set_bucket_tags.py b/set_tags/set_bucket_tags.py
index 020925a..6dae4f6 100644
--- a/set_tags/set_bucket_tags.py
+++ b/set_tags/set_bucket_tags.py
@@ -49,7 +49,7 @@ def apply_tags(name, tags):
 @helper.create
 @helper.update
 def create_or_update(event, context):
-  '''Handles customm resource create and update events'''
+  '''Handles custom resource create and update events'''
   log.debug('Received event: ' + json.dumps(event, sort_keys=False))
   log.info('Start Lambda processing')
   bucket_name = get_bucket_name(event)
@@ -58,7 +58,11 @@ def create_or_update(event, context):
   synapse_tags = utils.get_synapse_tags(synapse_owner_id)
   # put_bucket_tagging is a replace operation.  need to give it all
   # tags otherwise it will remove existing tags not in the list
-  all_tags = list(bucket_tags + synapse_tags)
+  #
+  # In case of duplication, Synapse tags should replace existing
+  # bucket tags.
+  all_tags = utils.merge_tags(bucket_tags, synapse_tags)
+
   log.debug(f'Apply tags: {all_tags} to bucket {bucket_name}')
   apply_tags(bucket_name, all_tags)
 
diff --git a/set_tags/set_instance_tags.py b/set_tags/set_instance_tags.py
index 24efef3..5b36987 100644
--- a/set_tags/set_instance_tags.py
+++ b/set_tags/set_instance_tags.py
@@ -83,7 +83,12 @@ def create_or_update(event, context):
   extra_tags.append(provisioned_product_name_tag)
   access_approved_role_tag = utils.get_access_approved_role_tag(instance_tags)
   extra_tags.append(access_approved_role_tag)
-  all_tags = list(synapse_tags + extra_tags)
+  #
+  # In case of duplication, Synapse tags should replace existing
+  # bucket tags.
+  #
+  all_tags = utils.merge_tags(extra_tags, synapse_tags)
+
 
   volume_ids = get_volume_ids(instance_id)
   log.debug(f'Apply tags: {all_tags} to volume {volume_ids}')
diff --git a/set_tags/utils.py b/set_tags/utils.py
index 9fb94be..3275c19 100644
--- a/set_tags/utils.py
+++ b/set_tags/utils.py
@@ -311,3 +311,13 @@ def get_access_approved_role_tag(tags):
       return access_approved_role_tag
   else:
     raise ValueError(f'Expected to find {PRINCIPAL_ARN_TAG_KEY} in {tags}')
+
+def merge_tags(list1, list2):
+  '''Merge two lists of tags, the second overriding the first on key collisions
+  '''
+  unique_tags = format_tags_kv_kp(list1)
+  unique_tags.update(format_tags_kv_kp(list2))
+  result=[]
+  for entry in unique_tags:
+      result.append({'Key':entry,'Value':unique_tags[entry]})
+  return result
diff --git a/tests/unit/utils/test_merge_tags.py b/tests/unit/utils/test_merge_tags.py
new file mode 100644
index 0000000..c1715a0
--- /dev/null
+++ b/tests/unit/utils/test_merge_tags.py
@@ -0,0 +1,15 @@
+import unittest
+
+from set_tags import utils
+
+class TestMergeTags(unittest.TestCase):
+
+  def test_happy_case(self):
+    tags = []
+    result = utils.merge_tags([{'Key':'foo','Value':'bar'}],[{'Key':'foo2','Value':'bar2'}])
+    self.assertEqual(result, [{'Key':'foo','Value':'bar'},{'Key':'foo2','Value':'bar2'}])
+
+  def test_collision(self):
+    tags = []
+    result = utils.merge_tags([{'Key':'foo','Value':'bar'}],[{'Key':'foo','Value':'bar2'}])
+    self.assertEqual(result, [{'Key':'foo','Value':'bar2'}])