diff --git a/src/main/java/com/amazonaws/services/s3/AmazonS3Client.java b/src/main/java/com/amazonaws/services/s3/AmazonS3Client.java
index c8349157dba2..72f3d6d4f328 100644
--- a/src/main/java/com/amazonaws/services/s3/AmazonS3Client.java
+++ b/src/main/java/com/amazonaws/services/s3/AmazonS3Client.java
@@ -944,7 +944,8 @@ public PutObjectResult putObject(PutObjectRequest putObjectRequest)
             request.addHeader(Headers.STORAGE_CLASS, putObjectRequest.getStorageClass());
         }
 
-        if (metadata.getContentLength() <= 0) {
+        // Use internal interface to differentiate 0 from unset.
+        if (metadata.getRawMetadata().get(Headers.CONTENT_LENGTH) == null) {
             /*
              * There's nothing we can do except for let the HTTP client buffer
              * the input stream contents if the caller doesn't tell us how much