diff --git a/src/constant.rs b/src/constant.rs
index ef72e6efb94..f90ad534970 100644
--- a/src/constant.rs
+++ b/src/constant.rs
@@ -167,6 +167,7 @@ pub(crate) fn codegen_const_value<'tcx>(
     }
 
     match const_val {
+        ConstValue::ZST => unreachable!(), // we already handles ZST above
         ConstValue::Scalar(x) => match x {
             Scalar::Int(int) => {
                 if fx.clif_type(layout.ty).is_some() {