diff --git a/Sources/Future/Future.swift b/Sources/Future/Future.swift
index 178c489..0e941a4 100644
--- a/Sources/Future/Future.swift
+++ b/Sources/Future/Future.swift
@@ -22,8 +22,6 @@ import ExecutionContext
 
 public protocol FutureProtocol : MovableExecutionContextTenantProtocol {
     associatedtype Value
-    //Can not workaround as a protocol, because protocol can't set itself as a requirement
-    typealias SettledTenant = Future<Value>
     
     init(value:Value)
     init(error:Error)
diff --git a/Sources/Future/Signal.swift b/Sources/Future/Signal.swift
index 8620861..25db6b7 100644
--- a/Sources/Future/Signal.swift
+++ b/Sources/Future/Signal.swift
@@ -21,7 +21,7 @@ import Result
 import Event
 
 public extension SignalStream {
-    public func flatMap<A, F : FutureProtocol>(_ f:@escaping (Payload)->F) -> SignalStream<Result<A, AnyError>> where F.Value == A {
+    public func flatMap<A, F : FutureProtocol>(_ f:@escaping (Payload)->F) -> SignalStream<Result<A, AnyError>> where F.Value == A, F.SettledTenant == Future<A> {
         let context = self.context
         return SignalStream<Result<A, AnyError>>(context: context, advise: { fun in
             self.chain { sig, payload in