diff --git a/parallel_hashmap/phmap_dump.h b/parallel_hashmap/phmap_dump.h
index aebf523..2eff9af 100644
--- a/parallel_hashmap/phmap_dump.h
+++ b/parallel_hashmap/phmap_dump.h
@@ -44,6 +44,8 @@ namespace priv {
 
 #if !defined(PHMAP_NON_DETERMINISTIC) && !defined(PHMAP_DISABLE_DUMP)
 
+static constexpr size_t s_version_base = std::numeric_limits<size_t>::max() - 10;
+static constexpr size_t s_version = s_version_base;
 // ------------------------------------------------------------------------
 // dump/load for raw_hash_set
 // ------------------------------------------------------------------------
@@ -53,6 +55,7 @@ bool raw_hash_set<Policy, Hash, Eq, Alloc>::phmap_dump(OutputArchive& ar) const
     static_assert(type_traits_internal::IsTriviallyCopyable<value_type>::value,
                     "value_type should be trivially copyable");
 
+    ar.saveBinary(&s_version, sizeof(size_t));
     ar.saveBinary(&size_, sizeof(size_t));
     ar.saveBinary(&capacity_, sizeof(size_t));
     if (size_ == 0)
@@ -69,7 +72,15 @@ bool raw_hash_set<Policy, Hash, Eq, Alloc>::phmap_load(InputArchive& ar) {
     static_assert(type_traits_internal::IsTriviallyCopyable<value_type>::value,
                     "value_type should be trivially copyable");
     raw_hash_set<Policy, Hash, Eq, Alloc>().swap(*this); // clear any existing content
-    ar.loadBinary(&size_, sizeof(size_t));
+
+    size_t version = 0;
+    ar.loadBinary(&version, sizeof(size_t));
+    if (version < s_version_base) {
+        // we didn't store the version, version actually contains the size
+        size_ = version;
+    } else {
+        ar.loadBinary(&size_, sizeof(size_t));
+    }
     ar.loadBinary(&capacity_, sizeof(size_t));
 
     if (capacity_) {
@@ -80,7 +91,9 @@ bool raw_hash_set<Policy, Hash, Eq, Alloc>::phmap_load(InputArchive& ar) {
         return true;
     ar.loadBinary(ctrl_,  sizeof(ctrl_t) * (capacity_ + Group::kWidth + 1));
     ar.loadBinary(slots_, sizeof(slot_type) * capacity_);
-    ar.loadBinary(&growth_left(), sizeof(size_t));
+    if (version == s_version_base) {
+        ar.loadBinary(&growth_left(), sizeof(size_t));
+    }
     return true;
 }