diff --git a/parallel_hashmap/phmap.h b/parallel_hashmap/phmap.h
index a211c56..2b7ddb8 100644
--- a/parallel_hashmap/phmap.h
+++ b/parallel_hashmap/phmap.h
@@ -1498,7 +1498,7 @@ public:
 
 #ifndef PHMAP_NON_DETERMINISTIC
     template<typename OutputArchive>
-    bool dump(OutputArchive&);
+    bool dump(OutputArchive&) const;
 
     template<typename InputArchive>
     bool load(InputArchive&);
@@ -3113,7 +3113,7 @@ public:
 
 #ifndef PHMAP_NON_DETERMINISTIC
     template<typename OutputArchive>
-    bool dump(OutputArchive& ar);
+    bool dump(OutputArchive& ar) const;
 
     template<typename InputArchive>
     bool load(InputArchive& ar);
diff --git a/parallel_hashmap/phmap_dump.h b/parallel_hashmap/phmap_dump.h
index 1c49057..0f3127a 100644
--- a/parallel_hashmap/phmap_dump.h
+++ b/parallel_hashmap/phmap_dump.h
@@ -47,7 +47,7 @@ namespace container_internal {
 // ------------------------------------------------------------------------
 template <class Policy, class Hash, class Eq, class Alloc>
 template<typename OutputArchive>
-bool raw_hash_set<Policy, Hash, Eq, Alloc>::dump(OutputArchive& ar) {
+bool raw_hash_set<Policy, Hash, Eq, Alloc>::dump(OutputArchive& ar) const {
     static_assert(type_traits_internal::IsTriviallyCopyable<value_type>::value,
                     "value_type should be trivially copyable");
 
@@ -117,7 +117,7 @@ template <size_t N,
           class Mtx_,
           class Policy, class Hash, class Eq, class Alloc>
 template<typename OutputArchive>
-bool parallel_hash_set<N, RefSet, Mtx_, Policy, Hash, Eq, Alloc>::dump(OutputArchive& ar) {
+bool parallel_hash_set<N, RefSet, Mtx_, Policy, Hash, Eq, Alloc>::dump(OutputArchive& ar) const {
     static_assert(type_traits_internal::IsTriviallyCopyable<value_type>::value,
                     "value_type should be trivially copyable");