diff --git a/gen3workflow/routes/s3.py b/gen3workflow/routes/s3.py
index 1d47d58..03f57f1 100644
--- a/gen3workflow/routes/s3.py
+++ b/gen3workflow/routes/s3.py
@@ -109,24 +109,17 @@ async def s3_endpoint(path: str, request: Request):
     region = config["USER_BUCKETS_REGION"]
     service = "s3"
 
-    # generate the request headers:
-    # - first, copy all the headers from the original request.
-    headers = dict(request.headers)
-    # - remove the `authorization` header: it contains a Gen3 token instead of an AWS IAM key.
-    #   The new `authorization` header will be added _after_ generating the signature.
-    headers.pop("authorization")
-    # - overwrite the `x-amz-content-sha256` header value with the body hash. When this header is
-    #   set to "STREAMING-AWS4-HMAC-SHA256-PAYLOAD" in the original request (payload sent over
-    #   multiple chunks), we replace it with the body hash (because I couldn't get the signing to
-    #   work for "STREAMING-AWS4-HMAC-SHA256-PAYLOAD" - I believe it requires using the signature
-    #   from the previous chunk).
-    #   NOTE: This may cause issues when large files are _actually_ uploaded over multiple chunks.
-    headers["x-amz-content-sha256"] = body_hash
-    # - remove the `content-md5` header: when the `x-amz-content-sha256` header is overwritten (see
-    #   above), the original `content-md5` value becomes incorrect. It's not required in V4 signing.
-    headers.pop("content-md5", None)
-    # - replace the `host` header, since we are re-signing and sending to a different host.
-    headers["host"] = f"{user_bucket}.s3.amazonaws.com"
+    # generate the request headers.
+    # overwrite the original `x-amz-content-sha256` header value with the body hash. When this
+    # header is set to "STREAMING-AWS4-HMAC-SHA256-PAYLOAD" in the original request (payload sent
+    # over multiple chunks), we still replace it with the body hash (because I couldn't get the
+    # signing to work for "STREAMING-AWS4-HMAC-SHA256-PAYLOAD" - I believe it requires using the signature from the previous chunk).
+    # NOTE: This may cause issues when large files are _actually_ uploaded over multiple chunks.
+    headers = {
+        "host": f"{user_bucket}.s3.amazonaws.com",
+        "x-amz-content-sha256": body_hash,
+        "x-amz-date": timestamp,
+    }
 
     # get AWS credentials from the configuration or the current assumed role session
     if config["S3_ENDPOINTS_AWS_ACCESS_KEY_ID"]: