diff --git a/packages/forms/src/directives/shared.ts b/packages/forms/src/directives/shared.ts
index 282be9901a..f40274a653 100644
--- a/packages/forms/src/directives/shared.ts
+++ b/packages/forms/src/directives/shared.ts
@@ -140,12 +140,12 @@ function _throwError(dir: AbstractControlDirective, message: string): void {
   throw new Error(`${message} ${messageEnd}`);
 }
 
-export function composeValidators(validators: Array<Validator|Function>): ValidatorFn|null {
+export function composeValidators(validators: Array<Validator|ValidatorFn>): ValidatorFn|null {
   return validators != null ? Validators.compose(validators.map(normalizeValidator)) : null;
 }
 
-export function composeAsyncValidators(validators: Array<Validator|Function>): AsyncValidatorFn|
-    null {
+export function composeAsyncValidators(validators: Array<AsyncValidator|AsyncValidatorFn>):
+    AsyncValidatorFn|null {
   return validators != null ? Validators.composeAsync(validators.map(normalizeAsyncValidator)) :
                               null;
 }
diff --git a/packages/forms/src/model.ts b/packages/forms/src/model.ts
index 0b446b2b18..04d7e6a25e 100644
--- a/packages/forms/src/model.ts
+++ b/packages/forms/src/model.ts
@@ -52,7 +52,7 @@ function _find(control: AbstractControl, path: Array<string|number>| string, del
   }
   if (path instanceof Array && (path.length === 0)) return null;
 
-  return (<Array<string|number>>path).reduce((v: AbstractControl, name) => {
+  return (<Array<string|number>>path).reduce((v: AbstractControl | null, name) => {
     if (v instanceof FormGroup) {
       return v.controls.hasOwnProperty(name as string) ? v.controls[name] : null;
     }