diff --git a/extensions/cookie/nsPermissionManager.cpp b/extensions/cookie/nsPermissionManager.cpp
index db9514902773..6192c4575e53 100644
--- a/extensions/cookie/nsPermissionManager.cpp
+++ b/extensions/cookie/nsPermissionManager.cpp
@@ -306,7 +306,7 @@ public:
   /**
    * @param aManager The owning manager.
    */
-  DeleteFromMozHostListener(nsPermissionManager* aManager);
+  explicit DeleteFromMozHostListener(nsPermissionManager* aManager);
 
 protected:
   nsRefPtr<nsPermissionManager> mManager;
diff --git a/extensions/cookie/nsPermissionManager.h b/extensions/cookie/nsPermissionManager.h
index cdf39657cbdb..ec8bac866118 100644
--- a/extensions/cookie/nsPermissionManager.h
+++ b/extensions/cookie/nsPermissionManager.h
@@ -67,7 +67,7 @@ public:
   class PermissionKey
   {
   public:
-    PermissionKey(nsIPrincipal* aPrincipal);
+    explicit PermissionKey(nsIPrincipal* aPrincipal);
     PermissionKey(const nsACString& aHost,
                   uint32_t aAppId,
                   bool aIsInBrowserElement)
@@ -109,7 +109,7 @@ public:
   class PermissionHashKey : public nsRefPtrHashKey<PermissionKey>
   {
   public:
-    PermissionHashKey(const PermissionKey* aPermissionKey)
+    explicit PermissionHashKey(const PermissionKey* aPermissionKey)
       : nsRefPtrHashKey<PermissionKey>(aPermissionKey)
     {}