diff --git a/packages/animations/src/players/animation_player.ts b/packages/animations/src/players/animation_player.ts
index d88f733b19..de3dfb4ffa 100644
--- a/packages/animations/src/players/animation_player.ts
+++ b/packages/animations/src/players/animation_player.ts
@@ -26,7 +26,7 @@ export interface AnimationPlayer {
   finish(): void;
   destroy(): void;
   reset(): void;
-  setPosition(position: number): void;
+  setPosition(p: any /** TODO #9100 */): void;
   getPosition(): number;
   parentPlayer: AnimationPlayer|null;
   readonly totalTime: number;
@@ -93,7 +93,7 @@ export class NoopAnimationPlayer implements AnimationPlayer {
     }
   }
   reset(): void {}
-  setPosition(position: number): void {}
+  setPosition(p: number): void {}
   getPosition(): number { return 0; }
 
   /* @internal */
diff --git a/tools/public_api_guard/animations/animations.d.ts b/tools/public_api_guard/animations/animations.d.ts
index b0f5a005b0..07f51a54f8 100644
--- a/tools/public_api_guard/animations/animations.d.ts
+++ b/tools/public_api_guard/animations/animations.d.ts
@@ -115,7 +115,7 @@ export interface AnimationPlayer {
     play(): void;
     reset(): void;
     restart(): void;
-    setPosition(position: number): void;
+    setPosition(p: any): void;
 }
 
 /** @experimental */
@@ -216,7 +216,7 @@ export declare class NoopAnimationPlayer implements AnimationPlayer {
     play(): void;
     reset(): void;
     restart(): void;
-    setPosition(position: number): void;
+    setPosition(p: number): void;
 }
 
 /** @experimental */