diff --git a/hash.c b/hash.c
index 42f2f993fb8de8..9c3164c96afdd4 100644
--- a/hash.c
+++ b/hash.c
@@ -4425,6 +4425,14 @@ rb_ident_hash_new(void)
     return hash;
 }
 
+VALUE
+rb_ident_hash_new_with_size(st_index_t size)
+{
+    VALUE hash = rb_hash_new();
+    RHASH_ST_TABLE_SET(hash, st_init_table_with_size(&identhash, size));
+    return hash;
+}
+
 st_table *
 rb_init_identtable(void)
 {
diff --git a/internal/hash.h b/internal/hash.h
index e1f83d5018eceb..f274cbbbd6a21c 100644
--- a/internal/hash.h
+++ b/internal/hash.h
@@ -83,6 +83,7 @@ int rb_hash_stlike_delete(VALUE hash, st_data_t *pkey, st_data_t *pval);
 int rb_hash_stlike_foreach_with_replace(VALUE hash, st_foreach_check_callback_func *func, st_update_callback_func *replace, st_data_t arg);
 int rb_hash_stlike_update(VALUE hash, st_data_t key, st_update_callback_func *func, st_data_t arg);
 extern st_table *rb_hash_st_table(VALUE hash);
+VALUE rb_ident_hash_new_with_size(st_index_t size);
 
 static inline unsigned RHASH_AR_TABLE_SIZE_RAW(VALUE h);
 static inline VALUE RHASH_IFNONE(VALUE h);