diff --git a/packages/core/src/Visitor.ts b/packages/core/src/Visitor.ts
index 14173cfdd358..7ca5332c89b3 100644
--- a/packages/core/src/Visitor.ts
+++ b/packages/core/src/Visitor.ts
@@ -885,7 +885,7 @@ export class Visitor {
         return n;
     }
 
-    visitTsFnParameters(params: TsFnParameter[]): TsFnParameter[] {
+    visitTsFnParameters(params: TsFnParameter[] = []): TsFnParameter[] {
         return params.map(this.visitTsFnParameter.bind(this));
     }