diff --git a/modules/@angular/compiler/src/shadow_css.ts b/modules/@angular/compiler/src/shadow_css.ts
index e15f58b105..0abf47876a 100644
--- a/modules/@angular/compiler/src/shadow_css.ts
+++ b/modules/@angular/compiler/src/shadow_css.ts
@@ -509,7 +509,7 @@ export class CssRule {
   constructor(public selector: string, public content: string) {}
 }
 
-export function processRules(input: string, ruleCallback: Function): string {
+export function processRules(input: string, ruleCallback: (rule: CssRule) => CssRule): string {
   const inputWithEscapedBlocks = escapeBlocks(input);
   let nextBlockIndex = 0;
   return inputWithEscapedBlocks.escapedString.replace(_ruleRe, function(...m: string[]) {
diff --git a/modules/@angular/compiler/test/shadow_css_spec.ts b/modules/@angular/compiler/test/shadow_css_spec.ts
index 3750f8b004..63b1e8845a 100644
--- a/modules/@angular/compiler/test/shadow_css_spec.ts
+++ b/modules/@angular/compiler/test/shadow_css_spec.ts
@@ -207,8 +207,8 @@ export function main() {
   describe('processRules', () => {
     describe('parse rules', () => {
       function captureRules(input: string): CssRule[] {
-        const result: any[] /** TODO #9100 */ = [];
-        processRules(input, (cssRule: any /** TODO #9100 */) => {
+        const result: CssRule[] = [];
+        processRules(input, (cssRule) => {
           result.push(cssRule);
           return cssRule;
         });
@@ -239,15 +239,15 @@ export function main() {
     describe('modify rules', () => {
       it('should allow to change the selector while preserving whitespaces', () => {
         expect(processRules(
-                   '@import a; b {c {d}} e {f}', (cssRule: any /** TODO #9100 */) => new CssRule(
-                                                     cssRule.selector + '2', cssRule.content)))
+                   '@import a; b {c {d}} e {f}',
+                   (cssRule: CssRule) => new CssRule(cssRule.selector + '2', cssRule.content)))
             .toEqual('@import a2; b2 {c {d}} e2 {f}');
       });
 
       it('should allow to change the content', () => {
         expect(processRules(
-                   'a {b}', (cssRule: any /** TODO #9100 */) =>
-                                new CssRule(cssRule.selector, cssRule.content + '2')))
+                   'a {b}',
+                   (cssRule: CssRule) => new CssRule(cssRule.selector, cssRule.content + '2')))
             .toEqual('a {b2}');
       });
     });