diff --git a/elab_expr.cc b/elab_expr.cc
index 699c4f5d5..3901b5723 100644
--- a/elab_expr.cc
+++ b/elab_expr.cc
@@ -2535,7 +2535,13 @@ NetExpr* PECastSize::elaborate_expr(Design*des, NetScope*scope,
       ivl_assert(*this, size_);
       ivl_assert(*this, base_);
 
-      NetExpr*sub = base_->elaborate_expr(des, scope, base_->expr_width(), flags);
+        // When changing size, a cast behaves exactly like an assignment,
+        // so the result size affects the final expression width.
+      unsigned cast_width = base_->expr_width();
+      if (cast_width < expr_width_)
+            cast_width = expr_width_;
+
+      NetExpr*sub = base_->elaborate_expr(des, scope, cast_width, flags);
 
 	// Perform the cast. The extension method (zero/sign), if needed,
 	// depends on the type of the base expression.