diff --git a/cmd/signature-v4.go b/cmd/signature-v4.go
index a8e8af845..d1bd96ab4 100644
--- a/cmd/signature-v4.go
+++ b/cmd/signature-v4.go
@@ -354,7 +354,7 @@ func doesSignatureMatch(hashedPayload string, r *http.Request, validateRegion bo
 	for _, h := range signV4Values.SignedHeaders {
 		if h == "content-length" {
 			header = cloneHeader(req.Header)
-			header.Add("content-length", strconv.FormatInt(r.ContentLength, 10))
+			header.Set("content-length", strconv.FormatInt(r.ContentLength, 10))
 			break
 		}
 	}