diff --git a/tests/baselines/reference/fatarrowfunctionsErrors.types b/tests/baselines/reference/fatarrowfunctionsErrors.types
index 4a493734e09..36b123e338a 100644
--- a/tests/baselines/reference/fatarrowfunctionsErrors.types
+++ b/tests/baselines/reference/fatarrowfunctionsErrors.types
@@ -25,10 +25,10 @@ foo((x?)=>{return x;})
 foo((x=0)=>{return x;})
 >foo((x=0)=>{return x;}) : any
 >foo : any
->(x=0)=>{return x;} : (x?: number) => number
->x : number
+>(x=0)=>{return x;} : (x?: any) => any
+>x : any
 >0 : 0
->x : number
+>x : any
 
 var y = x:number => x*x;
 >y : any
diff --git a/tests/baselines/reference/fatarrowfunctionsOptionalArgs.types b/tests/baselines/reference/fatarrowfunctionsOptionalArgs.types
index e9ae9488b91..ed7438dd6a0 100644
--- a/tests/baselines/reference/fatarrowfunctionsOptionalArgs.types
+++ b/tests/baselines/reference/fatarrowfunctionsOptionalArgs.types
@@ -653,8 +653,8 @@ foo(
 >116 : 116
 
     (a = 0) => 117, 
->(a = 0) => 117 : (a?: number) => number
->a : number
+>(a = 0) => 117 : (a?: any) => number
+>a : any
 >0 : 0
 >117 : 117
 
@@ -670,9 +670,9 @@ foo(
 >119 : 119
 
     (a, b? = 0, ...c: number[]) => 120,
->(a, b? = 0, ...c: number[]) => 120 : (a: any, b?: number, ...c: number[]) => number
+>(a, b? = 0, ...c: number[]) => 120 : (a: any, b?: any, ...c: number[]) => number
 >a : any
->b : number
+>b : any
 >0 : 0
 >c : number[]
 >120 : 120
diff --git a/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors4.types b/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors4.types
index 18860e274ca..7496677a194 100644
--- a/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors4.types
+++ b/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors4.types
@@ -88,8 +88,8 @@
 >116 : 116
 
         (a = 0) => 117, 
->(a = 0) => 117 : (a?: number) => number
->a : number
+>(a = 0) => 117 : (a?: any) => number
+>a : any
 >0 : 0
 >117 : 117
 
@@ -105,9 +105,9 @@
 >119 : 119
 
         (a, b? = 0, ...c: number[]) => 120,
->(a, b? = 0, ...c: number[]) => 120 : (a: any, b?: number, ...c: number[]) => number
+>(a, b? = 0, ...c: number[]) => 120 : (a: any, b?: any, ...c: number[]) => number
 >a : any
->b : number
+>b : any
 >0 : 0
 >c : number[]
 >120 : 120