diff --git a/Value/DictionaryByValue.cs b/Value/DictionaryByValue.cs
index 2b6b1ea..186ce7e 100644
--- a/Value/DictionaryByValue.cs
+++ b/Value/DictionaryByValue.cs
@@ -27,7 +27,7 @@ namespace Value.Shared
     /// <remarks>This type is not thread-safe (for hashcode updates).</remarks>
     /// <typeparam name="K">The type of keys in the dictionary.</typeparam>
     /// <typeparam name="V">The type of values in the dictionary.</typeparam>
-    public class DictionaryByValue<K, V> : EquatableByValueWithoutOrder<DictionaryByValue<K, V>>, IDictionary<K, V>
+    public class DictionaryByValue<K, V> : EquatableByValueWithoutOrder<DictionaryByValue<K, V>>, IDictionary<K, V>, IReadOnlyDictionary<K, V>
     {
         private readonly IDictionary<K, V> dictionary;
 
@@ -132,5 +132,9 @@ public V this[K key]
         public ICollection<K> Keys => dictionary.Keys;
 
         public ICollection<V> Values => dictionary.Values;
+
+        IEnumerable<K> IReadOnlyDictionary<K, V>.Keys => dictionary.Keys;
+
+        IEnumerable<V> IReadOnlyDictionary<K, V>.Values => dictionary.Values;
     }
 }
\ No newline at end of file
diff --git a/Value/ListByValue.cs b/Value/ListByValue.cs
index 296016a..b0b9fba 100644
--- a/Value/ListByValue.cs
+++ b/Value/ListByValue.cs
@@ -27,7 +27,7 @@ namespace Value
     /// </summary>
     /// <remarks>This type is not thread-safe (for hashcode updates).</remarks>
     /// <typeparam name="T">Type of the listed items.</typeparam>
-    public class ListByValue<T> : EquatableByValue<ListByValue<T>>, IList<T>
+    public class ListByValue<T> : EquatableByValue<ListByValue<T>>, IList<T>, IReadOnlyList<T>
     {
         private readonly IList<T> list;