diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
index ecc4a13..3feee8f 100644
--- a/include/polarssl/bignum.h
+++ b/include/polarssl/bignum.h
@@ -167,8 +167,8 @@
            #define POLARSSL_HAVE_UDBL
          #endif
        #endif
-    #endif
-  #endif
+    #endif /* !POLARSSL_HAVE_INT32 && __GNUC__ && 64-bit platform */
+  #endif /* !POLARSSL_HAVE_INT32 && _MSC_VER && _M_AMD64 */
 #endif /* POLARSSL_HAVE_INT16 */
 #endif /* POLARSSL_HAVE_INT8  */