diff --git a/caps/DomainPolicy.cpp b/caps/DomainPolicy.cpp
index 578d5963a866..960ce7844188 100644
--- a/caps/DomainPolicy.cpp
+++ b/caps/DomainPolicy.cpp
@@ -147,7 +147,7 @@ NS_IMETHODIMP
 DomainSet::Add(nsIURI* aDomain) {
   nsCOMPtr<nsIURI> clone = GetCanonicalClone(aDomain);
   NS_ENSURE_TRUE(clone, NS_ERROR_FAILURE);
-  mHashTable.PutEntry(clone);
+  mHashTable.Insert(clone);
   if (XRE_IsParentProcess()) {
     return BroadcastDomainSetChange(mType, ADD_DOMAIN, aDomain);
   }
@@ -159,7 +159,7 @@ NS_IMETHODIMP
 DomainSet::Remove(nsIURI* aDomain) {
   nsCOMPtr<nsIURI> clone = GetCanonicalClone(aDomain);
   NS_ENSURE_TRUE(clone, NS_ERROR_FAILURE);
-  mHashTable.RemoveEntry(clone);
+  mHashTable.Remove(clone);
   if (XRE_IsParentProcess()) {
     return BroadcastDomainSetChange(mType, REMOVE_DOMAIN, aDomain);
   }
@@ -215,10 +215,7 @@ DomainSet::ContainsSuperDomain(nsIURI* aDomain, bool* aContains) {
 }
 
 void DomainSet::CloneSet(nsTArray<RefPtr<nsIURI>>* aDomains) {
-  for (auto iter = mHashTable.Iter(); !iter.Done(); iter.Next()) {
-    nsIURI* key = iter.Get()->GetKey();
-    aDomains->AppendElement(key);
-  }
+  AppendToArray(*aDomains, mHashTable);
 }
 
 } /* namespace mozilla */
diff --git a/caps/DomainPolicy.h b/caps/DomainPolicy.h
index 105b7fc1a07d..24fe3b93956b 100644
--- a/caps/DomainPolicy.h
+++ b/caps/DomainPolicy.h
@@ -8,7 +8,7 @@
 #define DomainPolicy_h__
 
 #include "nsIDomainPolicy.h"
-#include "nsTHashtable.h"
+#include "nsTHashSet.h"
 #include "nsURIHashKey.h"
 
 namespace mozilla {
@@ -40,7 +40,7 @@ class DomainSet final : public nsIDomainSet {
 
  protected:
   virtual ~DomainSet() {}
-  nsTHashtable<nsURIHashKey> mHashTable;
+  nsTHashSet<nsURIHashKey> mHashTable;
   DomainSetType mType;
 };