diff --git a/net-core/Ical.Net/Serialization/DataTypes/RecurrencePatternSerializer.cs b/net-core/Ical.Net/Serialization/DataTypes/RecurrencePatternSerializer.cs
index 5bb506f38..18e4a3968 100644
--- a/net-core/Ical.Net/Serialization/DataTypes/RecurrencePatternSerializer.cs
+++ b/net-core/Ical.Net/Serialization/DataTypes/RecurrencePatternSerializer.cs
@@ -75,6 +75,14 @@ public virtual void CheckMutuallyExclusive<T, TU>(string name1, string name2, T
             {
                 return;
             }
+
+            // For some reason GetField("MinValue") sometimes returns 'null' when the obj is an int
+            // Casting the object to an int and directly checking for MinValue works though.
+            if (obj1 is int c && c == int.MinValue)
+            {
+                return;
+            }
+
             // If the object is MinValue instead of its default, consider
             // that to be unassigned.