diff --git a/src/configurable.rs b/src/configurable.rs
index 0a6e5f60..6be5c249 100644
--- a/src/configurable.rs
+++ b/src/configurable.rs
@@ -90,6 +90,79 @@ where
     }
 }
 
+pub struct Fn2NewConfigurableService<F, S, Err, Fut, Cfg>
+where
+    S: Service,
+    F: Fn(Cfg) -> Fut,
+    Fut: IntoFuture<Item = S, Error = Err>,
+{
+    f: F,
+    err: marker::PhantomData<Err>,
+    cfg: marker::PhantomData<Cfg>,
+    fut: marker::PhantomData<Fut>,
+    s: marker::PhantomData<S>,
+}
+
+impl<F, S, Err, Fut, Cfg> Fn2NewConfigurableService<F, S, Err, Fut, Cfg>
+where
+    S: Service,
+    F: Fn(Cfg) -> Fut + 'static,
+    Fut: IntoFuture<Item = S, Error = Err>,
+{
+    fn new(f: F) -> Self {
+        Fn2NewConfigurableService{
+            f,
+            err: marker::PhantomData,
+            cfg: marker::PhantomData,
+            fut: marker::PhantomData,
+            s: marker::PhantomData
+        }
+    }
+}
+
+impl<F, S, Err, Fut, Cfg>
+    IntoNewConfigurableService<Fn2NewConfigurableService<F, S, Err, Fut, Cfg>>
+    for F
+where
+    S: Service,
+    F: Fn(Cfg) -> Fut + 'static,
+    Fut: IntoFuture<Item = S, Error = Err>,
+{
+    fn into_new_service(self) -> Fn2NewConfigurableService<F, S, Err, Fut, Cfg> {
+        Fn2NewConfigurableService::new(self)
+    }
+}
+
+impl<F, S, Err, Fut, Cfg> Clone for Fn2NewConfigurableService<F, S, Err, Fut, Cfg>
+where
+    S: Service,
+    F: Fn(Cfg) -> Fut + Clone + 'static,
+    Fut: IntoFuture<Item = S, Error = Err>,
+{
+    fn clone(&self) -> Self {
+        Self::new(self.f.clone())
+    }
+}
+
+impl<F, S, Err, Fut, Cfg> NewConfigurableService for Fn2NewConfigurableService<F, S, Err, Fut, Cfg>
+where
+    S: Service,
+    F: Fn(Cfg) -> Fut,
+    Fut: IntoFuture<Item = S, Error = Err>,
+{
+    type Request = S::Request;
+    type Response = S::Response;
+    type Error = S::Error;
+    type Service = S;
+    type Config = Cfg;
+    type InitError = Err;
+    type Future = Fut::Future;
+
+    fn new_service(&self, cfg: Cfg) -> Self::Future {
+        (self.f)(cfg).into_future()
+    }
+}
+
 pub struct FnNewConfigurableService<F, Req, Resp, Err, IErr, Fut, Cfg>
 where
     F: Fn(Req) -> Fut,
diff --git a/src/lib.rs b/src/lib.rs
index c90d0041..1abeff3c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -60,7 +60,7 @@ pub mod service;
 pub mod ssl;
 mod worker;
 
-pub use configurable::NewConfigurableService;
+pub use configurable::{NewConfigurableService, IntoNewConfigurableService};
 pub use connector::{Connector, ConnectorError};
 pub use server::Server;
 pub use service::{IntoNewService, IntoService, NewServiceExt};
diff --git a/src/service.rs b/src/service.rs
index 5ead53ce..b655f0e7 100644
--- a/src/service.rs
+++ b/src/service.rs
@@ -521,12 +521,16 @@ where
     type Error = B::InitError;
 
     fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
-        if let Async::Ready(service) = self.fut_a.poll()? {
-            self.a = Some(service);
+        if self.a.is_none() {
+            if let Async::Ready(service) = self.fut_a.poll()? {
+                self.a = Some(service);
+            }
         }
 
-        if let Async::Ready(service) = self.fut_b.poll()? {
-            self.b = Some(service);
+        if self.b.is_none() {
+            if let Async::Ready(service) = self.fut_b.poll()? {
+                self.b = Some(service);
+            }
         }
 
         if self.a.is_some() && self.b.is_some() {