diff --git a/Sources/CombineTraits/ImmediatePublisher.swift b/Sources/CombineTraits/ImmediatePublisher.swift
index ab92d72..6c8de7b 100644
--- a/Sources/CombineTraits/ImmediatePublisher.swift
+++ b/Sources/CombineTraits/ImmediatePublisher.swift
@@ -81,7 +81,7 @@ import Foundation
 ///
 ///         // Fails with the given error.
 ///         AnyImmediatePublisher.fail(error)
-public protocol ImmediatePublisher: Publisher { }
+public protocol ImmediatePublisher<Output, Failure>: Publisher { }
 
 extension ImmediatePublisher {
     /// Wraps this immediate publisher with a type eraser.
diff --git a/Sources/CombineTraits/MaybePublisher.swift b/Sources/CombineTraits/MaybePublisher.swift
index d93b58c..32afb47 100644
--- a/Sources/CombineTraits/MaybePublisher.swift
+++ b/Sources/CombineTraits/MaybePublisher.swift
@@ -105,7 +105,7 @@ import Foundation
 ///
 ///         // Never publishes any value, never completes.
 ///         AnyMaybePublisher.never()
-public protocol MaybePublisher: Publisher { }
+public protocol MaybePublisher<Output, Failure>: Publisher { }
 
 extension MaybePublisher {
     /// Wraps this maybe publisher with a type eraser.
diff --git a/Sources/CombineTraits/SinglePublisher.swift b/Sources/CombineTraits/SinglePublisher.swift
index 466459a..d8639ae 100644
--- a/Sources/CombineTraits/SinglePublisher.swift
+++ b/Sources/CombineTraits/SinglePublisher.swift
@@ -103,7 +103,7 @@ import Foundation
 ///
 ///         // Never publishes any value, never completes.
 ///         AnySinglePublisher.never()
-public protocol SinglePublisher: MaybePublisher { }
+public protocol SinglePublisher<Output, Failure>: MaybePublisher { }
 
 extension SinglePublisher {
     /// Wraps this single publisher with a type eraser.