diff --git a/api_guard/dist/types/index.d.ts b/api_guard/dist/types/index.d.ts
index b1a2717d71..c237c227f5 100644
--- a/api_guard/dist/types/index.d.ts
+++ b/api_guard/dist/types/index.d.ts
@@ -435,8 +435,7 @@ export declare class Observable<T> implements Subscribable<T> {
     pipe<A, B, C, D, E, F, G, H>(op1: OperatorFunction<T, A>, op2: OperatorFunction<A, B>, op3: OperatorFunction<B, C>, op4: OperatorFunction<C, D>, op5: OperatorFunction<D, E>, op6: OperatorFunction<E, F>, op7: OperatorFunction<F, G>, op8: OperatorFunction<G, H>): Observable<H>;
     pipe<A, B, C, D, E, F, G, H, I>(op1: OperatorFunction<T, A>, op2: OperatorFunction<A, B>, op3: OperatorFunction<B, C>, op4: OperatorFunction<C, D>, op5: OperatorFunction<D, E>, op6: OperatorFunction<E, F>, op7: OperatorFunction<F, G>, op8: OperatorFunction<G, H>, op9: OperatorFunction<H, I>): Observable<I>;
     pipe<A, B, C, D, E, F, G, H, I>(op1: OperatorFunction<T, A>, op2: OperatorFunction<A, B>, op3: OperatorFunction<B, C>, op4: OperatorFunction<C, D>, op5: OperatorFunction<D, E>, op6: OperatorFunction<E, F>, op7: OperatorFunction<F, G>, op8: OperatorFunction<G, H>, op9: OperatorFunction<H, I>, ...operations: OperatorFunction<any, any>[]): Observable<unknown>;
-    subscribe(observer?: Partial<Observer<T>>): Subscription;
-    subscribe(next: (value: T) => void): Subscription;
+    subscribe(observerOrNext?: Partial<Observer<T>> | ((value: T) => void)): Subscription;
     subscribe(next?: ((value: T) => void) | null, error?: ((error: any) => void) | null, complete?: (() => void) | null): Subscription;
     toPromise(): Promise<T | undefined>;
     toPromise(PromiseCtor: typeof Promise): Promise<T | undefined>;
@@ -714,8 +713,7 @@ export declare function takeWhile<T, S extends T>(predicate: (value: T, index: n
 export declare function takeWhile<T, S extends T>(predicate: (value: T, index: number) => value is S, inclusive: false): OperatorFunction<T, S>;
 export declare function takeWhile<T>(predicate: (value: T, index: number) => boolean, inclusive?: boolean): MonoTypeOperatorFunction<T>;
 
-export declare function tap<T>(observer?: Partial<TapObserver<T>>): MonoTypeOperatorFunction<T>;
-export declare function tap<T>(next: (value: T) => void): MonoTypeOperatorFunction<T>;
+export declare function tap<T>(observerOrNext?: Partial<TapObserver<T>> | ((value: T) => void)): MonoTypeOperatorFunction<T>;
 export declare function tap<T>(next?: ((value: T) => void) | null, error?: ((error: any) => void) | null, complete?: (() => void) | null): MonoTypeOperatorFunction<T>;
 
 export declare type TeardownLogic = Subscription | Unsubscribable | (() => void) | void;
diff --git a/api_guard/dist/types/operators/index.d.ts b/api_guard/dist/types/operators/index.d.ts
index 162aeb5e70..963e5dcb55 100644
--- a/api_guard/dist/types/operators/index.d.ts
+++ b/api_guard/dist/types/operators/index.d.ts
@@ -283,8 +283,7 @@ export declare function takeWhile<T, S extends T>(predicate: (value: T, index: n
 export declare function takeWhile<T, S extends T>(predicate: (value: T, index: number) => value is S, inclusive: false): OperatorFunction<T, S>;
 export declare function takeWhile<T>(predicate: (value: T, index: number) => boolean, inclusive?: boolean): MonoTypeOperatorFunction<T>;
 
-export declare function tap<T>(observer?: Partial<TapObserver<T>>): MonoTypeOperatorFunction<T>;
-export declare function tap<T>(next: (value: T) => void): MonoTypeOperatorFunction<T>;
+export declare function tap<T>(observerOrNext?: Partial<TapObserver<T>> | ((value: T) => void)): MonoTypeOperatorFunction<T>;
 export declare function tap<T>(next?: ((value: T) => void) | null, error?: ((error: any) => void) | null, complete?: (() => void) | null): MonoTypeOperatorFunction<T>;
 
 export declare function throttle<T>(durationSelector: (value: T) => ObservableInput<any>, { leading, trailing }?: ThrottleConfig): MonoTypeOperatorFunction<T>;
diff --git a/src/internal/Observable.ts b/src/internal/Observable.ts
index abab383605..9a7e903be3 100644
--- a/src/internal/Observable.ts
+++ b/src/internal/Observable.ts
@@ -74,8 +74,7 @@ export class Observable<T> implements Subscribable<T> {
     return observable;
   }
 
-  subscribe(observer?: Partial<Observer<T>>): Subscription;
-  subscribe(next: (value: T) => void): Subscription;
+  subscribe(observerOrNext?: Partial<Observer<T>> | ((value: T) => void)): Subscription;
   /** @deprecated Instead of passing separate callback arguments, use an observer argument. Signatures taking separate callback arguments will be removed in v8. Details: https://rxjs.dev/deprecations/subscribe-arguments */
   subscribe(next?: ((value: T) => void) | null, error?: ((error: any) => void) | null, complete?: (() => void) | null): Subscription;
   /**
diff --git a/src/internal/operators/tap.ts b/src/internal/operators/tap.ts
index 364d4ca3eb..feaefcf70d 100644
--- a/src/internal/operators/tap.ts
+++ b/src/internal/operators/tap.ts
@@ -9,9 +9,7 @@ export interface TapObserver<T> extends Observer<T> {
   unsubscribe: () => void;
   finalize: () => void;
 }
-
-export function tap<T>(observer?: Partial<TapObserver<T>>): MonoTypeOperatorFunction<T>;
-export function tap<T>(next: (value: T) => void): MonoTypeOperatorFunction<T>;
+export function tap<T>(observerOrNext?: Partial<TapObserver<T>> | ((value: T) => void)): MonoTypeOperatorFunction<T>;
 /** @deprecated Instead of passing separate callback arguments, use an observer argument. Signatures taking separate callback arguments will be removed in v8. Details: https://rxjs.dev/deprecations/subscribe-arguments */
 export function tap<T>(
   next?: ((value: T) => void) | null,