diff --git a/Sources/Combine/PublisherType+Publisher.swift b/Sources/Combine/PublisherType+Publisher.swift
index d1d04cea..a996ff75 100644
--- a/Sources/Combine/PublisherType+Publisher.swift
+++ b/Sources/Combine/PublisherType+Publisher.swift
@@ -3,6 +3,7 @@ import Combine
 import Foundation
 import SwiftRex
 
+@available(iOS 13, watchOS 6, macOS 10.15, tvOS 13, *)
 extension PublisherType: Publisher {
     public typealias Output = Element
     public typealias Failure = ErrorType
@@ -23,6 +24,7 @@ extension PublisherType: Publisher {
     }
 }
 
+@available(iOS 13, watchOS 6, macOS 10.15, tvOS 13, *)
 extension Publisher {
     public func asPublisherType() -> PublisherType<Output, Failure> {
         return .init { (subscriber: SubscriberType<Output, Failure>) -> SwiftRex.Subscription in
diff --git a/Sources/Combine/ReplayLastSubjectType+BehaviorSubject.swift b/Sources/Combine/ReplayLastSubjectType+BehaviorSubject.swift
index 02ac2e2b..7382da8e 100644
--- a/Sources/Combine/ReplayLastSubjectType+BehaviorSubject.swift
+++ b/Sources/Combine/ReplayLastSubjectType+BehaviorSubject.swift
@@ -3,6 +3,7 @@ import Combine
 import Foundation
 import SwiftRex
 
+@available(iOS 13, watchOS 6, macOS 10.15, tvOS 13, *)
 extension ReplayLastSubjectType {
     public init(currentValueSubject: CurrentValueSubject<Element, ErrorType>) {
         self.init(
diff --git a/Sources/Combine/SubjectType+PassthroughSubject.swift b/Sources/Combine/SubjectType+PassthroughSubject.swift
index 0f25f966..6bf86e43 100644
--- a/Sources/Combine/SubjectType+PassthroughSubject.swift
+++ b/Sources/Combine/SubjectType+PassthroughSubject.swift
@@ -3,6 +3,7 @@ import Combine
 import Foundation
 import SwiftRex
 
+@available(iOS 13, watchOS 6, macOS 10.15, tvOS 13, *)
 extension SwiftRex.SubjectType {
     public init(passthroughSubject: PassthroughSubject<Element, ErrorType>) {
         self.init(
@@ -17,6 +18,7 @@ extension SwiftRex.SubjectType {
     }
 }
 
+@available(iOS 13, watchOS 6, macOS 10.15, tvOS 13, *)
 extension SwiftRex.SubjectType {
     public static func combine() -> SwiftRex.SubjectType<Element, ErrorType> {
         let passthroughSubject = PassthroughSubject<Element, ErrorType>()
diff --git a/Sources/Combine/SubscriberType+Subscriber.swift b/Sources/Combine/SubscriberType+Subscriber.swift
index 6dccfe45..cb3b9976 100644
--- a/Sources/Combine/SubscriberType+Subscriber.swift
+++ b/Sources/Combine/SubscriberType+Subscriber.swift
@@ -3,6 +3,7 @@ import Combine
 import Foundation
 import SwiftRex
 
+@available(iOS 13, watchOS 6, macOS 10.15, tvOS 13, *)
 extension SubscriberType: Subscriber {
     public var combineIdentifier: CombineIdentifier {
         CombineIdentifier()
@@ -26,6 +27,7 @@ extension SubscriberType: Subscriber {
     }
 }
 
+@available(iOS 13, watchOS 6, macOS 10.15, tvOS 13, *)
 extension Subscriber {
     public func asSubscriberType() -> SubscriberType<Self.Input, Self.Failure> {
         return SubscriberType<Self.Input, Self.Failure>(
diff --git a/Sources/Combine/Subscription+Cancellable.swift b/Sources/Combine/Subscription+Cancellable.swift
index cdf3e424..7adccbca 100644
--- a/Sources/Combine/Subscription+Cancellable.swift
+++ b/Sources/Combine/Subscription+Cancellable.swift
@@ -3,12 +3,14 @@ import Combine
 import Foundation
 import SwiftRex
 
+@available(iOS 13, watchOS 6, macOS 10.15, tvOS 13, *)
 extension SwiftRex.Subscription {
     public func asCancellable() -> CancellableSubscription {
         return CancellableSubscription(subscription: self)
     }
 }
 
+@available(iOS 13, watchOS 6, macOS 10.15, tvOS 13, *)
 public class CancellableSubscription: Cancellable, SwiftRex.Subscription, Combine.Subscription {
     public func request(_ demand: Subscribers.Demand) {
         // No support for backpressure