diff --git a/Octokit/Helpers/Net45CompatibilityShim.cs b/Octokit/Helpers/Net45CompatibilityShim.cs
new file mode 100644
index 00000000..acb99bfd
--- /dev/null
+++ b/Octokit/Helpers/Net45CompatibilityShim.cs
@@ -0,0 +1,103 @@
+// ----------------------------------------------------
+// THIS WHOLE File CAN GO AWAY WHEN WE TARGET 4.5 ONLY
+// ----------------------------------------------------
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Octokit
+{
+    [SuppressMessage("Microsoft.Naming", "CA1710:IdentifiersShouldHaveCorrectSuffix")]
+    [SuppressMessage("Microsoft.Naming", "CA1711:IdentifiersShouldNotHaveIncorrectSuffix")]
+    public interface IReadOnlyDictionary<TKey, TValue> : IReadOnlyCollection<KeyValuePair<TKey, TValue>>
+    {
+        bool ContainsKey(TKey key);
+        bool TryGetValue(TKey key, out TValue value);
+
+        TValue this[TKey key] { get; }
+        IEnumerable<TKey> Keys { get; }
+        IEnumerable<TValue> Values { get; }
+    }
+
+    public interface IReadOnlyCollection<out T> : IEnumerable<T>
+    {
+        int Count { get; }
+    }
+
+    public class ReadOnlyCollection<TItem> : IReadOnlyCollection<TItem>
+    {
+        readonly List<TItem> _source;
+
+        public ReadOnlyCollection(IEnumerable<TItem> source)
+        {
+            _source = new List<TItem>(source);
+        }
+
+        public IEnumerator<TItem> GetEnumerator()
+        {
+            return _source.GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        public int Count
+        {
+            get { return _source.Count; }
+        }
+    }
+
+    [SuppressMessage("Microsoft.Naming", "CA1710:IdentifiersShouldHaveCorrectSuffix")]
+    [SuppressMessage("Microsoft.Naming", "CA1711:IdentifiersShouldNotHaveIncorrectSuffix")]
+    public class ReadOnlyDictionary<TKey, TValue> : IReadOnlyDictionary<TKey, TValue>
+    {
+        readonly IDictionary<TKey, TValue> _source;
+
+        public ReadOnlyDictionary(IDictionary<TKey, TValue> source)
+        {
+            _source = new Dictionary<TKey, TValue>(source);
+        }
+
+        public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
+        {
+            return _source.GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        public int Count
+        {
+            get { return _source.Count; }
+        }
+
+        public bool ContainsKey(TKey key)
+        {
+            return _source.ContainsKey(key);
+        }
+
+        public bool TryGetValue(TKey key, out TValue value)
+        {
+            return _source.TryGetValue(key, out value);
+        }
+
+        public TValue this[TKey key]
+        {
+            get { return _source[key]; }
+        }
+
+        public IEnumerable<TKey> Keys
+        {
+            get { return _source.Keys; }
+        }
+
+        public IEnumerable<TValue> Values
+        {
+            get { return _source.Values; }
+        }
+    }
+}