diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
index fac39be0b..e02db3f76 100644
--- a/include/polarssl/bignum.h
+++ b/include/polarssl/bignum.h
@@ -42,6 +42,7 @@ typedef  INT16  int16_t;
 typedef UINT16 uint16_t;
 #endif
 typedef  INT32  int32_t;
+typedef  INT64  int64_t;
 typedef UINT32 uint32_t;
 typedef UINT64 uint64_t;
 #else