diff --git a/ext/mbstring/oniguruma/regint.h b/ext/mbstring/oniguruma/regint.h
index 7ab233aeb4a..f06154dda16 100644
--- a/ext/mbstring/oniguruma/regint.h
+++ b/ext/mbstring/oniguruma/regint.h
@@ -793,7 +793,12 @@ extern int  onig_is_code_in_cc_len P_((int enclen, OnigCodePoint code, CClassNod
 
 /* strend hash */
 typedef void hash_table_type;
+#ifdef _WIN32
+# include <windows.h>
+typedef ULONG_PTR hash_data_type;
+#else
 typedef unsigned long hash_data_type;
+#endif
 
 extern hash_table_type* onig_st_init_strend_table_with_size P_((int size));
 extern int onig_st_lookup_strend P_((hash_table_type* table, const UChar* str_key, const UChar* end_key, hash_data_type *value));