diff --git a/Pilz.Net/Api/ApiParameterCollection.cs b/Pilz.Net/Api/ApiParameterCollection.cs
index 84ede96..c966ec9 100644
--- a/Pilz.Net/Api/ApiParameterCollection.cs
+++ b/Pilz.Net/Api/ApiParameterCollection.cs
@@ -2,13 +2,13 @@
 
 namespace Pilz.Net.Api;
 
-public class ApiParameterCollection : Dictionary<string, object>
+public class ApiParameterCollection : Dictionary<string, object?>
 {
     public ApiParameterCollection()
     {
     }
 
-    public ApiParameterCollection(IDictionary<string, object> source)
+    public ApiParameterCollection(IDictionary<string, object?> source)
     {
         source.ForEach(kvp => Add(kvp.Key, kvp.Value));
     }