diff --git a/Library/OcGuardLib/NativeOverflow.c b/Library/OcGuardLib/NativeOverflow.c
index a5c0146b..edad4054 100644
--- a/Library/OcGuardLib/NativeOverflow.c
+++ b/Library/OcGuardLib/NativeOverflow.c
@@ -16,19 +16,24 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 
 **/
 
+#include <Base.h>
+
 #include <Library/OcGuardLib.h>
 
 //
 // Currently no architectures provide UINTN and INTN different from 32-bit or 64-bit
 // integers. For this reason they are the only variants supported and are enforced here.
-// The lib must be C99-compliant, thus no _Static_assert.
 //
 
-typedef BOOLEAN SignedIntnMustBe32or64[sizeof (INTN) == sizeof (INT64)
-  || sizeof (INTN) == sizeof (INT32) ? 1 : -1];
+STATIC_ASSERT (
+  sizeof (INTN) == sizeof (INT64) || sizeof (INTN) == sizeof (INT32),
+  "INTN must be 32 or 64 Bits wide."
+  );
 
-typedef BOOLEAN UnsignedIntnMustBe32or64[sizeof (UINTN) == sizeof (UINT64)
-  || sizeof (UINTN) == sizeof (UINT32) ? 1 : -1];
+STATIC_ASSERT (
+  sizeof (UINTN) == sizeof (UINT64) || sizeof (UINTN) == sizeof (UINT32),
+  "UINTN must be 32 or 64 Bits wide."
+  );
 
 BOOLEAN
 (OcOverflowAddUN) (