diff --git a/js/public/HashTable.h b/js/public/HashTable.h
index c8ad21d95ba4..1a5e814ff826 100644
--- a/js/public/HashTable.h
+++ b/js/public/HashTable.h
@@ -17,6 +17,7 @@
 #include "mozilla/ReentrancyGuard.h"
 #include "mozilla/TemplateLib.h"
 #include "mozilla/TypeTraits.h"
+#include "mozilla/UniquePtr.h"
 
 #include "js/Utility.h"
 
@@ -586,6 +587,25 @@ template <class T>
 struct DefaultHasher<T*> : PointerHasher<T*, mozilla::tl::FloorLog2<sizeof(void*)>::value>
 {};
 
+// Specialize hashing policy for mozilla::UniquePtr<T> to proxy the UniquePtr's
+// raw pointer to PointerHasher.
+template <class T>
+struct DefaultHasher<mozilla::UniquePtr<T>>
+{
+    using Lookup = mozilla::UniquePtr<T>;
+    using PtrHasher = PointerHasher<T*, mozilla::tl::FloorLog2<sizeof(void*)>::value>;
+
+    static HashNumber hash(const Lookup& l) {
+        return PtrHasher::hash(l.get());
+    }
+    static bool match(const mozilla::UniquePtr<T>& k, const Lookup& l) {
+        return PtrHasher::match(k.get(), l.get());
+    }
+    static void rekey(mozilla::UniquePtr<T>& k, mozilla::UniquePtr<T>&& newKey) {
+        k = mozilla::Move(newKey);
+    }
+};
+
 // For doubles, we can xor the two uint32s.
 template <>
 struct DefaultHasher<double>