diff --git a/libmproxy/flow.py b/libmproxy/flow.py
index dd43a24f3..5f5cad4c0 100644
--- a/libmproxy/flow.py
+++ b/libmproxy/flow.py
@@ -538,7 +538,7 @@ class Response(HTTPMsg):
         self.headers = ODictCaseless._from_state(state["headers"])
         self.content = state["content"]
         self.timestamp = state["timestamp"]
-        self.cert = state["cert"]
+        self.cert = certutils.SSLCert.from_pem(state["cert"]) if state["cert"] else None
 
     def _get_state(self):
         return dict(
diff --git a/test/test_flow.py b/test/test_flow.py
index 1394a6685..1dd44dd2d 100644
--- a/test/test_flow.py
+++ b/test/test_flow.py
@@ -192,6 +192,13 @@ class TestFlow:
         f.revert()
         assert f.request.content == "foo"
 
+    def test_backup_idempotence(self):
+        f = tutils.tflow_full()
+        f.backup()
+        f.revert()
+        f.backup()
+        f.revert()
+
     def test_getset_state(self):
         f = tutils.tflow()
         f.response = tutils.tresp(f.request)