diff --git a/CryptoPkg/Library/OpensslLib/OpensslStub/SslNull.c b/CryptoPkg/Library/OpensslLib/OpensslStub/SslNull.c
index 49f1405bc0..9f659728fe 100644
--- a/CryptoPkg/Library/OpensslLib/OpensslStub/SslNull.c
+++ b/CryptoPkg/Library/OpensslLib/OpensslStub/SslNull.c
@@ -80,10 +80,10 @@ SSL_CTX_new (
   return NULL;
 }
 
-unsigned long
+uint64_t
 SSL_CTX_set_options (
-  SSL_CTX        *ctx,
-  unsigned long  op
+  SSL_CTX   *ctx,
+  uint64_t  op
   )
 {
   ASSERT (FALSE);