diff --git a/tests/cases/compiler/defaultParameterAddsUndefinedWithStrictNullChecks.ts b/tests/cases/compiler/defaultParameterAddsUndefinedWithStrictNullChecks.ts
index 17c9f063882..eb11a85ac09 100644
--- a/tests/cases/compiler/defaultParameterAddsUndefinedWithStrictNullChecks.ts
+++ b/tests/cases/compiler/defaultParameterAddsUndefinedWithStrictNullChecks.ts
@@ -1,4 +1,5 @@
 // @strictNullChecks: true
+// @declaration: true
 function f(addUndefined1 = "J", addUndefined2?: number) {
     return addUndefined1.length + (addUndefined2 || 0);
 }
@@ -7,3 +8,30 @@ function g(addUndefined = "J", addDefined: number) {
 }
 let total = f() + f('a', 1) + f('b') + f(undefined, 2);
 total = g('c', 3) + g(undefined, 4);
+
+function foo1(x: string = "string", b: number) {
+    x.length;
+}
+
+function foo2(x: string | undefined = "string", b: number) {
+    x.length; // ok, should be narrowed to string
+}
+
+function foo3(x = "string", b: number) {
+    x.length; // ok, should be narrowed to string
+}
+
+function foo4(x: string | undefined, b: number) {
+   x.length; // error, Object is possibly 'undefined'
+}
+
+foo1(undefined, 1);
+foo2(undefined, 1);
+foo3(undefined, 1);
+foo4(undefined, 1);
+
+
+// all four functions should have `x: string| undefined` in their type
+// .d.ts should have `T | undefined` for all of them
+// foo2 to have x be initialized on the first line
+// need to remove special-case code to allow calling foo1(undefined) for x: string = "string"