diff --git a/src/WireMock.Net/Serialization/MappingConverter.cs b/src/WireMock.Net/Serialization/MappingConverter.cs
index 0ad9f9ec..4cc45e75 100644
--- a/src/WireMock.Net/Serialization/MappingConverter.cs
+++ b/src/WireMock.Net/Serialization/MappingConverter.cs
@@ -77,7 +77,7 @@ namespace WireMock.Serialization
                 },
                 Response = new ResponseModel
                 {
-                    Delay = response.Delay?.Milliseconds
+                    Delay = (int?) response.Delay?.TotalMilliseconds
                 }
             };