diff --git a/src/api/js/src/high-level/high-level.ts b/src/api/js/src/high-level/high-level.ts
index 897cd01f72e..74a3a9d2dcf 100644
--- a/src/api/js/src/high-level/high-level.ts
+++ b/src/api/js/src/high-level/high-level.ts
@@ -503,7 +503,7 @@ export function createApi(Z3: Z3Core): Z3HighLevel {
     ///////////////////////////////
 
     async function simplify(e : Expr<Name>) {
-       return _toExpr(check(Z3.simplify(contextPtr, e)));
+       return _toExpr(check(Z3.simplify(contextPtr, e.ast)));
     }
 
     /////////////