diff --git a/src/operators/defaultIfEmpty.ts b/src/operators/defaultIfEmpty.ts
index 4d78419359..0088ec4bae 100644
--- a/src/operators/defaultIfEmpty.ts
+++ b/src/operators/defaultIfEmpty.ts
@@ -1,10 +1,10 @@
 import { Operator } from '../Operator';
 import { Observable } from '../Observable';
 import { Subscriber } from '../Subscriber';
-import { OperatorFunction } from '../interfaces';
+import { OperatorFunction, MonoTypeOperatorFunction } from '../interfaces';
 
 /* tslint:disable:max-line-length */
-export function defaultIfEmpty<T>(defaultValue?: T): OperatorFunction<T, T>;
+export function defaultIfEmpty<T>(defaultValue?: T): MonoTypeOperatorFunction<T>;
 export function defaultIfEmpty<T, R>(defaultValue?: R): OperatorFunction<T, T | R>;
 /* tslint:enable:max-line-length */
 
diff --git a/src/operators/filter.ts b/src/operators/filter.ts
index 117fcaf543..541d6622fd 100644
--- a/src/operators/filter.ts
+++ b/src/operators/filter.ts
@@ -2,13 +2,13 @@ import { Operator } from '../Operator';
 import { Subscriber } from '../Subscriber';
 import { Observable } from '../Observable';
 import { TeardownLogic } from '../Subscription';
-import { OperatorFunction } from '../interfaces';
+import { OperatorFunction, MonoTypeOperatorFunction } from '../interfaces';
 
 /* tslint:disable:max-line-length */
 export function filter<T, S extends T>(predicate: (value: T, index: number) => value is S,
                                        thisArg?: any): OperatorFunction<T, S>;
 export function filter<T>(predicate: (value: T, index: number) => boolean,
-                          thisArg?: any): OperatorFunction<T, T>;
+                          thisArg?: any): MonoTypeOperatorFunction<T>;
 /* tslint:enable:max-line-length */
 
 /**
@@ -51,7 +51,7 @@ export function filter<T>(predicate: (value: T, index: number) => boolean,
  * @owner Observable
  */
 export function filter<T>(predicate: (value: T, index: number) => boolean,
-                          thisArg?: any): OperatorFunction<T, T> {
+                          thisArg?: any): MonoTypeOperatorFunction<T> {
   return function filterOperatorFunction(source: Observable<T>): Observable<T> {
     return source.lift(new FilterOperator(predicate, thisArg));
   };
diff --git a/src/operators/max.ts b/src/operators/max.ts
index c3693fc577..0b8b9bafcd 100644
--- a/src/operators/max.ts
+++ b/src/operators/max.ts
@@ -1,5 +1,5 @@
 import { reduce } from './reduce';
-import { OperatorFunction } from '../interfaces';
+import { MonoTypeOperatorFunction } from '../interfaces';
 
 /**
  * The Max operator operates on an Observable that emits numbers (or items that can be compared with a provided function),
@@ -32,7 +32,7 @@ import { OperatorFunction } from '../interfaces';
  * @method max
  * @owner Observable
  */
-export function max<T>(comparer?: (x: T, y: T) => number): OperatorFunction<T, T> {
+export function max<T>(comparer?: (x: T, y: T) => number): MonoTypeOperatorFunction<T> {
   const max: (x: T, y: T) => T = (typeof comparer === 'function')
     ? (x, y) => comparer(x, y) > 0 ? x : y
     : (x, y) => x > y ? x : y;
diff --git a/src/operators/min.ts b/src/operators/min.ts
index 75e9f58ac6..99cdf8c1b4 100644
--- a/src/operators/min.ts
+++ b/src/operators/min.ts
@@ -1,5 +1,5 @@
 import { reduce } from './reduce';
-import { OperatorFunction } from '../interfaces';
+import { MonoTypeOperatorFunction } from '../interfaces';
 
 /**
  * The Min operator operates on an Observable that emits numbers (or items that can be compared with a provided function),
@@ -32,7 +32,7 @@ import { OperatorFunction } from '../interfaces';
  * @method min
  * @owner Observable
  */
-export function min<T>(comparer?: (x: T, y: T) => number): OperatorFunction<T, T> {
+export function min<T>(comparer?: (x: T, y: T) => number): MonoTypeOperatorFunction<T> {
   const min: (x: T, y: T) => T = (typeof comparer === 'function')
     ? (x, y) => comparer(x, y) < 0 ? x : y
     : (x, y) => x < y ? x : y;
diff --git a/src/operators/reduce.ts b/src/operators/reduce.ts
index bb05114d6f..04f043274e 100644
--- a/src/operators/reduce.ts
+++ b/src/operators/reduce.ts
@@ -2,11 +2,11 @@ import { Observable } from '../Observable';
 import { scan } from './scan';
 import { takeLast } from './takeLast';
 import { defaultIfEmpty } from './defaultIfEmpty';
-import { OperatorFunction } from '../interfaces';
+import { OperatorFunction, MonoTypeOperatorFunction } from '../interfaces';
 import { compose } from '../util/compose';
 
 /* tslint:disable:max-line-length */
-export function reduce<T>(accumulator: (acc: T, value: T, index: number) => T, seed?: T): OperatorFunction<T, T>;
+export function reduce<T>(accumulator: (acc: T, value: T, index: number) => T, seed?: T): MonoTypeOperatorFunction<T>;
 export function reduce<T>(accumulator: (acc: T[], value: T, index: number) => T[], seed: T[]): OperatorFunction<T, T[]>;
 export function reduce<T, R>(accumulator: (acc: R, value: T, index: number) => R, seed?: R): OperatorFunction<T, R>;
 /* tslint:enable:max-line-length */
diff --git a/src/operators/scan.ts b/src/operators/scan.ts
index 4dc6046a45..0e97976d37 100644
--- a/src/operators/scan.ts
+++ b/src/operators/scan.ts
@@ -1,10 +1,10 @@
 import { Operator } from '../Operator';
 import { Observable } from '../Observable';
 import { Subscriber } from '../Subscriber';
-import { OperatorFunction } from '../interfaces';
+import { OperatorFunction, MonoTypeOperatorFunction } from '../interfaces';
 
 /* tslint:disable:max-line-length */
-export function scan<T>(accumulator: (acc: T, value: T, index: number) => T, seed?: T): OperatorFunction<T, T>;
+export function scan<T>(accumulator: (acc: T, value: T, index: number) => T, seed?: T): MonoTypeOperatorFunction<T>;
 export function scan<T>(accumulator: (acc: T[], value: T, index: number) => T[], seed?: T[]): OperatorFunction<T, T[]>;
 export function scan<T, R>(accumulator: (acc: R, value: T, index: number) => R, seed?: R): OperatorFunction<T, R>;
 /* tslint:enable:max-line-length */
diff --git a/src/operators/takeLast.ts b/src/operators/takeLast.ts
index e6e44d9cef..3e408b4da7 100644
--- a/src/operators/takeLast.ts
+++ b/src/operators/takeLast.ts
@@ -4,7 +4,7 @@ import { ArgumentOutOfRangeError } from '../util/ArgumentOutOfRangeError';
 import { EmptyObservable } from '../observable/EmptyObservable';
 import { Observable } from '../Observable';
 import { TeardownLogic } from '../Subscription';
-import { OperatorFunction } from '../interfaces';
+import { MonoTypeOperatorFunction } from '../interfaces';
 
 /**
  * Emits only the last `count` values emitted by the source Observable.
@@ -42,7 +42,7 @@ import { OperatorFunction } from '../interfaces';
  * @method takeLast
  * @owner Observable
  */
-export function takeLast<T>(count: number): OperatorFunction<T, T> {
+export function takeLast<T>(count: number): MonoTypeOperatorFunction<T> {
   return function takeLastOperatorFunction(source: Observable<T>): Observable<T> {
     if (count === 0) {
       return new EmptyObservable<T>();