diff --git a/lib/lib.es2015.core.d.ts b/lib/lib.es2015.core.d.ts
index c7c7afb821b..c92a44c2312 100644
--- a/lib/lib.es2015.core.d.ts
+++ b/lib/lib.es2015.core.d.ts
@@ -37,7 +37,7 @@ interface Array<T> {
       * @param thisArg If provided, it will be used as the this value for each invocation of
       * predicate. If it is not provided, undefined is used instead.
       */
-    findIndex(predicate: (value: T) => boolean, thisArg?: any): number;
+    findIndex(predicate: (value: T, index: number, obj: Array<T>) => boolean, thisArg?: any): number;
 
     /**
       * Returns the this object after filling the section identified by start and end with value
diff --git a/lib/lib.es6.d.ts b/lib/lib.es6.d.ts
index 8e9de3f4ec9..a7faa4789a6 100644
--- a/lib/lib.es6.d.ts
+++ b/lib/lib.es6.d.ts
@@ -4143,7 +4143,7 @@ interface Array<T> {
       * @param thisArg If provided, it will be used as the this value for each invocation of
       * predicate. If it is not provided, undefined is used instead.
       */
-    findIndex(predicate: (value: T) => boolean, thisArg?: any): number;
+    findIndex(predicate: (value: T, index: number, obj: Array<T>) => boolean, thisArg?: any): number;
 
     /**
       * Returns the this object after filling the section identified by start and end with value
diff --git a/src/lib/es2015.core.d.ts b/src/lib/es2015.core.d.ts
index 15fbb1b77c5..7395039b1c9 100644
--- a/src/lib/es2015.core.d.ts
+++ b/src/lib/es2015.core.d.ts
@@ -21,7 +21,7 @@ interface Array<T> {
       * @param thisArg If provided, it will be used as the this value for each invocation of
       * predicate. If it is not provided, undefined is used instead.
       */
-    findIndex(predicate: (value: T) => boolean, thisArg?: any): number;
+    findIndex(predicate: (value: T, index: number, obj: Array<T>) => boolean, thisArg?: any): number;
 
     /**
       * Returns the this object after filling the section identified by start and end with value
@@ -368,7 +368,7 @@ interface ReadonlyArray<T> {
     * @param thisArg If provided, it will be used as the this value for each invocation of
     * predicate. If it is not provided, undefined is used instead.
     */
-  findIndex(predicate: (value: T) => boolean, thisArg?: any): number;
+  findIndex(predicate: (value: T, index: number, obj: Array<T>) => boolean, thisArg?: any): number;
 }
 
 interface RegExp {