diff --git a/lodash/lodash.d.ts b/lodash/lodash.d.ts
index 97aeab757a..06b6d8e335 100644
--- a/lodash/lodash.d.ts
+++ b/lodash/lodash.d.ts
@@ -2823,12 +2823,22 @@ declare module _ {
 			callback?: (objectValue: Value, sourceValue: Value) => Value,
             thisArg?: any): Result;
 
+		/**
+		* @see _.assign
+		**/
+	extend<P, T extends P, S1 extends P, Value, Result extends P>(
+            object: T,
+            s1: S1,
+			callback?: (objectValue: Value, sourceValue: Value) => Value,
+            thisArg?: any): Result;
+
 		/**
 		* @see _.assign
 		**/
         extend<P, T extends P, S1 extends P, S2 extends P, Value, Result extends P>(
             object: T,
             s1: S1,
+            s2: S2,
 			callback?: (objectValue: Value, sourceValue: Value) => Value,
             thisArg?: any): Result;
 
@@ -2839,6 +2849,7 @@ declare module _ {
             object: T,
             s1: S1,
             s2: S2,
+            s3: S3,
 			callback?: (objectValue: Value, sourceValue: Value) => Value,
             thisArg?: any): Result;