diff --git a/src/multisets-lib/Multiset.scala b/src/multisets-lib/Multiset.scala
new file mode 100644
index 0000000000000000000000000000000000000000..91624ed2f6cdca171ada8c9145994f38051e99ae
--- /dev/null
+++ b/src/multisets-lib/Multiset.scala
@@ -0,0 +1,17 @@
+package scala.collection.immutable
+
+case class UnimplementedFeatureException() extends Exception
+
+object Multiset {
+  def empty[A] : Multiset[A] = throw UnimplementedFeatureException()
+  def apply[A](elems: A*) : Multiset[A] = throw UnimplementedFeatureException()
+}
+
+trait Multiset[A] {
+  def ** (that: Multiset[A]) : Multiset[A] = throw UnimplementedFeatureException()
+  def ++ (that: Multiset[A]) : Multiset[A] = throw UnimplementedFeatureException()
+  def +++ (that: Multiset[A]) : Multiset[A] = throw UnimplementedFeatureException()
+  def -- (that: Multiset[A]) : Multiset[A] = throw UnimplementedFeatureException()
+  def toSet : scala.collection.immutable.Set[A] = throw UnimplementedFeatureException()
+  def size : Int = throw UnimplementedFeatureException()
+}