diff --git a/moto/s3/responses.py b/moto/s3/responses.py
index 8120e35ea..79c0945ee 100644
--- a/moto/s3/responses.py
+++ b/moto/s3/responses.py
@@ -130,7 +130,7 @@ def _key_response(request, full_url, headers):
     if method == 'PUT':
         if 'x-amz-copy-source' in request.headers:
             # Copy key
-            src_bucket, src_key = request.headers.get("x-amz-copy-source").split("/",2)
+            src_bucket, src_key = request.headers.get("x-amz-copy-source").split("/",1)
             s3_backend.copy_key(src_bucket, src_key, bucket_name, key_name)
             template = Template(S3_OBJECT_COPY_RESPONSE)
             return template.render(key=src_key)