diff --git a/dotnet/Razorvine.Pyrolite/Pyrolite/Pickle/Internals/PicklerImplementation.cs b/dotnet/Razorvine.Pyrolite/Pyrolite/Pickle/Internals/PicklerImplementation.cs
index 0f8ee0e..cf55294 100644
--- a/dotnet/Razorvine.Pyrolite/Pyrolite/Pickle/Internals/PicklerImplementation.cs
+++ b/dotnet/Razorvine.Pyrolite/Pyrolite/Pickle/Internals/PicklerImplementation.cs
@@ -240,7 +240,10 @@ private bool dispatch(Type t, object o)
                         put_enumerable(v);
                         return true;
                     case IEnumerable v:
-                        put_enumerable(v);
+                        if (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(HashSet<>))
+                            put_set(v);
+                        else
+                            put_enumerable(v);
                         return true;
                 }
             }