Index: src/AST/Bitfield.hpp
===================================================================
--- src/AST/Bitfield.hpp	(revision 1346914ea47e0410d38c770b01303dae319282ea)
+++ src/AST/Bitfield.hpp	(revision 93744b58e740b700af32339b06e691f172b99706)
@@ -9,12 +9,13 @@
 // Author           : Aaron B. Moss
 // Created On       : Thu May 9 10:00:00 2019
-// Last Modified By : Aaron B. Moss
-// Last Modified On : Thu May 9 10:00:00 2019
-// Update Count     : 1
+// Last Modified By : Andrew Beach
+// Last Modified On : Wed Jun 5 10:00:00 2019
+// Update Count     : 2
 //
 
 #pragma once
 
-#include <strings.h>  // for ffs
+#include <strings.h>   // for ffs
+#include <type_traits> // for is_unsigned
 
 /// Make a type a bitfield.
@@ -24,7 +25,8 @@
 template<typename T>
 struct bitfield : public T {
-	static_assert(sizeof(T) == sizeof(unsigned int), "Type has incorrect size");
 	using T::val;
 	using val_t = decltype(val);
+	static_assert(sizeof(T) == sizeof(unsigned int), "Type has incorrect size");
+	static_assert(std::is_unsigned<val_t>::value, "Bitfield val field is not unsigned.");
 
 	constexpr bitfield() : T( 0 ) {}