diff --git a/s3tests/functional/test_s3.py b/s3tests/functional/test_s3.py
--- a/s3tests/functional/test_s3.py
+++ b/s3tests/functional/test_s3.py
@@ -20631,13 +20631,6 @@ def _test_copy_part_enc(file_size, source_mode_key, dest_mode_key, source_sc=Non
     })
 
     if dest_mode_key == 'sse-c':
-        # make sure api is verifying the SSE-C headers
-        e = assert_raises(ClientError, client.complete_multipart_upload,
-                          Bucket=dest_bucket_name, Key='testobj2',
-                          UploadId=upload_id, MultipartUpload={'Parts': parts})
-        status, _ = _get_status_and_error_code(e.response)
-        assert status == 400
-
         # and the key would be the same as the one used in upload part
         # use the source key to complete the upload
         # this is not allowed, so we expect an error
@@ -20649,6 +20642,10 @@ def _test_copy_part_enc(file_size, source_mode_key, dest_mode_key, source_sc=Non
         status, _ = _get_status_and_error_code(e.response)
         assert status == 400
 
+        # CompleteMultipartUpload does not require SSE-C headers. The upload
+        # metadata already identifies the key used for the uploaded parts.
+        complete_args = {}
+
     # complete the multipart upload
     response = client.complete_multipart_upload(
         Bucket=dest_bucket_name,