diff --git a/parallel_hashmap/phmap.h b/parallel_hashmap/phmap.h
index abcd6ae..fe88b05 100644
--- a/parallel_hashmap/phmap.h
+++ b/parallel_hashmap/phmap.h
@@ -135,6 +135,7 @@ void SwapAlloc(AllocType& lhs, AllocType& rhs,
   using std::swap;
   swap(lhs, rhs);
 }
+
 template <typename AllocType>
 void SwapAlloc(AllocType& /*lhs*/, AllocType& /*rhs*/,
                std::false_type /* propagate_on_container_swap */) {}
@@ -192,11 +193,16 @@ struct IsDecomposable<
 // TODO(alkis): Switch to std::is_nothrow_swappable when gcc/clang supports it.
 // --------------------------------------------------------------------------
 template <class T>
-constexpr bool IsNoThrowSwappable() {
+constexpr bool IsNoThrowSwappable(std::true_type = {} /* is_swappable */) {
     using std::swap;
     return noexcept(swap(std::declval<T&>(), std::declval<T&>()));
 }
 
+template <class T>
+constexpr bool IsNoThrowSwappable(std::false_type /* is_swappable */) {
+  return false;
+}
+
 // --------------------------------------------------------------------------
 template <typename T>
 int TrailingZeros(T x) {
@@ -1647,7 +1653,7 @@ public:
     void swap(raw_hash_set& that) noexcept(
         IsNoThrowSwappable<hasher>() && IsNoThrowSwappable<key_equal>() &&
         (!AllocTraits::propagate_on_container_swap::value ||
-         IsNoThrowSwappable<allocator_type>())) {
+         IsNoThrowSwappable<allocator_type>(typename AllocTraits::propagate_on_container_swap{}))) {
         using std::swap;
         swap(ctrl_, that.ctrl_);
         swap(slots_, that.slots_);
@@ -1657,12 +1663,7 @@ public:
         swap(hash_ref(), that.hash_ref());
         swap(eq_ref(), that.eq_ref());
         swap(infoz_, that.infoz_);
-        if (AllocTraits::propagate_on_container_swap::value) {
-            swap(alloc_ref(), that.alloc_ref());
-        } else {
-            // If the allocators do not compare equal it is officially undefined
-            // behavior. We choose to do nothing.
-        }
+        SwapAlloc(alloc_ref(), that.alloc_ref(), typename AllocTraits::propagate_on_container_swap{});
     }
 
 #if !defined(PHMAP_NON_DETERMINISTIC)
@@ -3485,7 +3486,7 @@ public:
     void swap(parallel_hash_set<N, RefSet, Mtx2_, Policy, Hash, Eq, Alloc>& that)
         noexcept(IsNoThrowSwappable<EmbeddedSet>() &&
                  (!AllocTraits::propagate_on_container_swap::value ||
-                  IsNoThrowSwappable<allocator_type>()))
+                  IsNoThrowSwappable<allocator_type>(typename AllocTraits::propagate_on_container_swap{})))
     {
         using std::swap;
         using Lockable2 = phmap::LockableImpl<Mtx2_>;