diff --git a/src/eval_context.rs b/src/eval_context.rs
index 244f50befa9..77d9d9b20cd 100644
--- a/src/eval_context.rs
+++ b/src/eval_context.rs
@@ -788,11 +788,15 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
                 self.write_value(val, dest, dest_ty)?;
             }
 
-            Box(ty) => {
+            NullaryOp(mir::NullOp::Box, ty) => {
                 let ptr = self.alloc_ptr(ty)?;
                 self.write_primval(dest, PrimVal::Ptr(ptr), dest_ty)?;
             }
 
+            NullaryOp(mir::NullOp::SizeOf, _ty) => {
+                unimplemented!()
+            }
+
             Cast(kind, ref operand, cast_ty) => {
                 debug_assert_eq!(self.monomorphize(cast_ty, self.substs()), dest_ty);
                 use rustc::mir::CastKind::*;