diff --git a/tests/integration/test_stubs.py b/tests/integration/test_stubs.py
index aa40004..745d64b 100644
--- a/tests/integration/test_stubs.py
+++ b/tests/integration/test_stubs.py
@@ -1,6 +1,8 @@
 import vcr
 import six.moves.http_client as httplib
 
+from assertions import assert_is_json
+
 
 def _headers_are_case_insensitive(host, port):
     conn = httplib.HTTPConnection(host, port)
@@ -44,3 +46,35 @@ def test_multiple_headers(tmpdir, httpbin):
         inside = _multiple_header_value(httpbin)
 
     assert outside == inside
+
+
+def test_original_decoded_response_is_not_modified(tmpdir, httpbin):
+    testfile = str(tmpdir.join('decoded_response.yml'))
+    host, port = httpbin.host, httpbin.port
+
+    conn = httplib.HTTPConnection(host, port)
+    conn.request('GET', '/gzip')
+    outside = conn.getresponse()
+
+    with vcr.use_cassette(testfile, decode_compressed_response=True):
+        conn = httplib.HTTPConnection(host, port)
+        conn.request('GET', '/gzip')
+        inside = conn.getresponse()
+
+        # Assert that we do not modify the original response while appending
+        # to the casssette.
+        assert 'gzip' == inside.headers['content-encoding']
+
+        # They should effectively be the same response.
+        assert inside.headers.items() == outside.getheaders()
+        assert inside.read() == outside.read()
+
+    # Even though the above are raw bytes, the JSON data should have been
+    # decoded and saved to the cassette.
+    with vcr.use_cassette(testfile):
+        conn = httplib.HTTPConnection(host, port)
+        conn.request('GET', '/gzip')
+        inside = conn.getresponse()
+
+        assert 'content-encoding' not in inside.headers
+        assert_is_json(inside.read())
diff --git a/vcr/filters.py b/vcr/filters.py
index db6c130..bd7e6c6 100644
--- a/vcr/filters.py
+++ b/vcr/filters.py
@@ -146,9 +146,11 @@ def decode_response(response):
         else:  # encoding == 'deflate'
             return zlib.decompress(body)
 
+    # Deepcopy here in case `headers` contain objects that could
+    # be mutated by a shallow copy and corrupt the real response.
+    response = copy.deepcopy(response)
     headers = CaseInsensitiveDict(response['headers'])
     if is_compressed(headers):
-        response = copy.deepcopy(response)
         encoding = headers['content-encoding'][0]
         headers['content-encoding'].remove(encoding)
         if not headers['content-encoding']: