diff --git a/tests/baselines/reference/defaultParameterAddsUndefinedWithStrictNullChecks.symbols b/tests/baselines/reference/defaultParameterAddsUndefinedWithStrictNullChecks.symbols
index 054291e602b..ae11720ed15 100644
--- a/tests/baselines/reference/defaultParameterAddsUndefinedWithStrictNullChecks.symbols
+++ b/tests/baselines/reference/defaultParameterAddsUndefinedWithStrictNullChecks.symbols
@@ -3,5 +3,84 @@ function f(addUndefined1 = "J", addUndefined2?: number) {
 >f : Symbol(f, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 0, 0))
 >addUndefined1 : Symbol(addUndefined1, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 0, 11))
 >addUndefined2 : Symbol(addUndefined2, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 0, 31))
+
+    return addUndefined1.length + (addUndefined2 || 0);
+>addUndefined1.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>addUndefined1 : Symbol(addUndefined1, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 0, 11))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>addUndefined2 : Symbol(addUndefined2, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 0, 31))
+}
+function g(addUndefined = "J", addDefined: number) {
+>g : Symbol(g, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 2, 1))
+>addUndefined : Symbol(addUndefined, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 3, 11))
+>addDefined : Symbol(addDefined, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 3, 30))
+
+    return addUndefined.length + addDefined;
+>addUndefined.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>addUndefined : Symbol(addUndefined, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 3, 11))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>addDefined : Symbol(addDefined, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 3, 30))
+}
+let total = f() + f('a', 1) + f('b') + f(undefined, 2);
+>total : Symbol(total, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 6, 3))
+>f : Symbol(f, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 0, 0))
+>f : Symbol(f, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 0, 0))
+>f : Symbol(f, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 0, 0))
+>f : Symbol(f, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 0, 0))
+>undefined : Symbol(undefined)
+
+total = g('c', 3) + g(undefined, 4);
+>total : Symbol(total, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 6, 3))
+>g : Symbol(g, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 2, 1))
+>g : Symbol(g, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 2, 1))
+>undefined : Symbol(undefined)
+
+function foo1(x: string = "string", b: number) {
+>foo1 : Symbol(foo1, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 7, 36))
+>x : Symbol(x, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 9, 14))
+>b : Symbol(b, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 9, 35))
+
+    x.length;
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 9, 14))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
 }
 
+function foo2(x: string | undefined = "string", b: number) {
+>foo2 : Symbol(foo2, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 11, 1))
+>x : Symbol(x, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 13, 14))
+>b : Symbol(b, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 13, 47))
+
+    x.length; // ok, should be narrowed to string
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 13, 14))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+}
+
+function foo3(x = "string", b: number) {
+>foo3 : Symbol(foo3, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 15, 1))
+>x : Symbol(x, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 17, 14))
+>b : Symbol(b, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 17, 27))
+
+    x.length; // ok, should be narrowed to string
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 17, 14))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+}
+
+foo1(undefined, 1);
+>foo1 : Symbol(foo1, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 7, 36))
+>undefined : Symbol(undefined)
+
+foo2(undefined, 1);
+>foo2 : Symbol(foo2, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 11, 1))
+>undefined : Symbol(undefined)
+
+foo3(undefined, 1);
+>foo3 : Symbol(foo3, Decl(defaultParameterAddsUndefinedWithStrictNullChecks.ts, 15, 1))
+>undefined : Symbol(undefined)
+
+
+// .d.ts should have `T | undefined` for all of them
+// need to remove special-case code to allow calling foo1(undefined) for x: string = "string"
+
diff --git a/tests/baselines/reference/defaultParameterAddsUndefinedWithStrictNullChecks.types b/tests/baselines/reference/defaultParameterAddsUndefinedWithStrictNullChecks.types
index af35394da56..29dac892689 100644
--- a/tests/baselines/reference/defaultParameterAddsUndefinedWithStrictNullChecks.types
+++ b/tests/baselines/reference/defaultParameterAddsUndefinedWithStrictNullChecks.types
@@ -1,8 +1,120 @@
 === tests/cases/compiler/defaultParameterAddsUndefinedWithStrictNullChecks.ts ===
 function f(addUndefined1 = "J", addUndefined2?: number) {
->f : (addUndefined1?: string | undefined, addUndefined2?: number | undefined) => void
+>f : (addUndefined1?: string | undefined, addUndefined2?: number | undefined) => number
 >addUndefined1 : string | undefined
 >"J" : "J"
 >addUndefined2 : number | undefined
+
+    return addUndefined1.length + (addUndefined2 || 0);
+>addUndefined1.length + (addUndefined2 || 0) : number
+>addUndefined1.length : number
+>addUndefined1 : string
+>length : number
+>(addUndefined2 || 0) : number
+>addUndefined2 || 0 : number
+>addUndefined2 : number | undefined
+>0 : 0
+}
+function g(addUndefined = "J", addDefined: number) {
+>g : (addUndefined: string | undefined, addDefined: number) => number
+>addUndefined : string | undefined
+>"J" : "J"
+>addDefined : number
+
+    return addUndefined.length + addDefined;
+>addUndefined.length + addDefined : number
+>addUndefined.length : number
+>addUndefined : string
+>length : number
+>addDefined : number
+}
+let total = f() + f('a', 1) + f('b') + f(undefined, 2);
+>total : number
+>f() + f('a', 1) + f('b') + f(undefined, 2) : number
+>f() + f('a', 1) + f('b') : number
+>f() + f('a', 1) : number
+>f() : number
+>f : (addUndefined1?: string | undefined, addUndefined2?: number | undefined) => number
+>f('a', 1) : number
+>f : (addUndefined1?: string | undefined, addUndefined2?: number | undefined) => number
+>'a' : "a"
+>1 : 1
+>f('b') : number
+>f : (addUndefined1?: string | undefined, addUndefined2?: number | undefined) => number
+>'b' : "b"
+>f(undefined, 2) : number
+>f : (addUndefined1?: string | undefined, addUndefined2?: number | undefined) => number
+>undefined : undefined
+>2 : 2
+
+total = g('c', 3) + g(undefined, 4);
+>total = g('c', 3) + g(undefined, 4) : number
+>total : number
+>g('c', 3) + g(undefined, 4) : number
+>g('c', 3) : number
+>g : (addUndefined: string | undefined, addDefined: number) => number
+>'c' : "c"
+>3 : 3
+>g(undefined, 4) : number
+>g : (addUndefined: string | undefined, addDefined: number) => number
+>undefined : undefined
+>4 : 4
+
+function foo1(x: string = "string", b: number) {
+>foo1 : (x: string | undefined, b: number) => void
+>x : string | undefined
+>"string" : "string"
+>b : number
+
+    x.length;
+>x.length : number
+>x : string
+>length : number
 }
 
+function foo2(x: string | undefined = "string", b: number) {
+>foo2 : (x: string | undefined, b: number) => void
+>x : string | undefined
+>"string" : "string"
+>b : number
+
+    x.length; // ok, should be narrowed to string
+>x.length : number
+>x : string
+>length : number
+}
+
+function foo3(x = "string", b: number) {
+>foo3 : (x: string | undefined, b: number) => void
+>x : string | undefined
+>"string" : "string"
+>b : number
+
+    x.length; // ok, should be narrowed to string
+>x.length : number
+>x : string
+>length : number
+}
+
+foo1(undefined, 1);
+>foo1(undefined, 1) : void
+>foo1 : (x: string | undefined, b: number) => void
+>undefined : undefined
+>1 : 1
+
+foo2(undefined, 1);
+>foo2(undefined, 1) : void
+>foo2 : (x: string | undefined, b: number) => void
+>undefined : undefined
+>1 : 1
+
+foo3(undefined, 1);
+>foo3(undefined, 1) : void
+>foo3 : (x: string | undefined, b: number) => void
+>undefined : undefined
+>1 : 1
+
+
+// .d.ts should have `T | undefined` for all of them
+// need to remove special-case code to allow calling foo1(undefined) for x: string = "string"
+
diff --git a/tests/cases/compiler/defaultParameterAddsUndefinedWithStrictNullChecks.ts b/tests/cases/compiler/defaultParameterAddsUndefinedWithStrictNullChecks.ts
index eb11a85ac09..f84e85286ff 100644
--- a/tests/cases/compiler/defaultParameterAddsUndefinedWithStrictNullChecks.ts
+++ b/tests/cases/compiler/defaultParameterAddsUndefinedWithStrictNullChecks.ts
@@ -21,17 +21,10 @@ 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"