diff --git a/source/Nuke.Utilities/Collections/Dictionary.AddDictionary.cs b/source/Nuke.Utilities/Collections/Dictionary.AddDictionary.cs
index b871e9198..40e8c9c52 100644
--- a/source/Nuke.Utilities/Collections/Dictionary.AddDictionary.cs
+++ b/source/Nuke.Utilities/Collections/Dictionary.AddDictionary.cs
@@ -17,14 +17,4 @@ public static TDictionary AddDictionary<TDictionary, TKey, TValue>(
             dictionary.AddPair(key, value);
         return dictionary;
     }
-
-    public static TDictionary AddDictionary<TDictionary, TKey, TValue>(
-        this TDictionary dictionary,
-        IReadOnlyDictionary<TKey, TValue> otherDictionary)
-        where TDictionary : IDictionary<TKey, TValue>
-    {
-        foreach (var (key, value) in otherDictionary)
-            dictionary.AddPair(key, value);
-        return dictionary;
-    }
 }
diff --git a/source/Nuke.Utilities/Collections/Dictionary.AsReadOnly.cs b/source/Nuke.Utilities/Collections/Dictionary.AsReadOnly.cs
index 8929f30d5..00a0a8f0b 100644
--- a/source/Nuke.Utilities/Collections/Dictionary.AsReadOnly.cs
+++ b/source/Nuke.Utilities/Collections/Dictionary.AsReadOnly.cs
@@ -2,6 +2,8 @@
 // Distributed under the MIT License.
 // https://github.com/nuke-build/nuke/blob/master/LICENSE
 
+#if NETSTANDARD2_0
+
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
@@ -16,3 +18,4 @@ public static IReadOnlyDictionary<TKey, TValue> AsReadOnly<TKey, TValue>(this ID
         return new ReadOnlyDictionary<TKey, TValue>(dictionary);
     }
 }
+#endif