diff --git a/pkgs/collection/lib/src/unmodifiable_wrappers.dart b/pkgs/collection/lib/src/unmodifiable_wrappers.dart
index 897ccdbc..78484ab0 100644
--- a/pkgs/collection/lib/src/unmodifiable_wrappers.dart
+++ b/pkgs/collection/lib/src/unmodifiable_wrappers.dart
@@ -193,4 +193,12 @@ abstract mixin class UnmodifiableMapMixin<K, V> implements Map<K, V> {
   /// operations that change the map are disallowed.
   @override
   void clear() => _throw();
+
+  /// Throws an [UnsupportedError].
+  @Deprecated('This will be removed at a later date.')
+  set first(dynamic _) => _throw();
+
+  /// Throws an [UnsupportedError].
+  @Deprecated('This will be removed at a later date.')
+  set last(dynamic _) => _throw();
 }