diff --git a/Sources/ObservableSet.swift b/Sources/ObservableSet.swift
index e5f2ad2..d9525aa 100644
--- a/Sources/ObservableSet.swift
+++ b/Sources/ObservableSet.swift
@@ -10,7 +10,7 @@ public typealias SetUpdate<Element: Hashable> = Update<SetChange<Element>>
 public typealias SetUpdateSource<Element: Hashable> = AnySource<Update<SetChange<Element>>>
 
 public protocol ObservableSetType: ObservableType where Change == SetChange<Element> {
-    associatedtype Element
+    associatedtype Element: Hashable
 
     typealias Base = Set<Element>