diff --git a/packages/core/src/runtime/quasivalue.ts b/packages/core/src/runtime/quasivalue.ts
index 2f621cb..c98e6a1 100644
--- a/packages/core/src/runtime/quasivalue.ts
+++ b/packages/core/src/runtime/quasivalue.ts
@@ -138,7 +138,7 @@ export function ctor(info: QuasiValueConstructorInfo, ... items: QuasiValue[]):
                     return p;
                 }
             }
-            throw new Error(`Missing named parameter ${stringify(b.name.description!)} to ${defNameStr}`);
+            return _;
         }
 
         function qPattern(p: Meta.Pattern<unknown>): QuasiValue {