diff --git a/src/service/make_service.rs b/src/service/make_service.rs
index f694e30cc5..0472d2f983 100644
--- a/src/service/make_service.rs
+++ b/src/service/make_service.rs
@@ -115,7 +115,7 @@ where
 /// ```
 pub fn make_service_fn<F, Ctx, Ret>(f: F) -> MakeServiceFn<F>
 where
-    F: Fn(&Ctx) -> Ret,
+    F: FnMut(&Ctx) -> Ret,
     Ret: IntoFuture,
 {
     MakeServiceFn {
@@ -130,7 +130,7 @@ pub struct MakeServiceFn<F> {
 
 impl<'c, F, Ctx, Ret, ReqBody, ResBody> MakeService<&'c Ctx> for MakeServiceFn<F>
 where
-    F: Fn(&Ctx) -> Ret,
+    F: FnMut(&Ctx) -> Ret,
     Ret: IntoFuture,
     Ret::Item: Service<ReqBody=ReqBody, ResBody=ResBody>,
     Ret::Error: Into<Box<StdError + Send + Sync>>,
diff --git a/src/service/service.rs b/src/service/service.rs
index 0f9d7e2020..53d3e166c9 100644
--- a/src/service/service.rs
+++ b/src/service/service.rs
@@ -51,7 +51,7 @@ pub trait Service {
 /// ```
 pub fn service_fn<F, R, S>(f: F) -> ServiceFn<F, R>
 where
-    F: Fn(Request<R>) -> S,
+    F: FnMut(Request<R>) -> S,
     S: IntoFuture,
 {
     ServiceFn {
@@ -75,7 +75,7 @@ where
 /// ```
 pub fn service_fn_ok<F, R, S>(f: F) -> ServiceFnOk<F, R>
 where
-    F: Fn(Request<R>) -> Response<S>,
+    F: FnMut(Request<R>) -> Response<S>,
     S: Payload,
 {
     ServiceFnOk {
@@ -92,7 +92,7 @@ pub struct ServiceFn<F, R> {
 
 impl<F, ReqBody, Ret, ResBody> Service for ServiceFn<F, ReqBody>
 where
-    F: Fn(Request<ReqBody>) -> Ret,
+    F: FnMut(Request<ReqBody>) -> Ret,
     ReqBody: Payload,
     Ret: IntoFuture<Item=Response<ResBody>>,
     Ret::Error: Into<Box<StdError + Send + Sync>>,
@@ -133,7 +133,7 @@ pub struct ServiceFnOk<F, R> {
 
 impl<F, ReqBody, ResBody> Service for ServiceFnOk<F, ReqBody>
 where
-    F: Fn(Request<ReqBody>) -> Response<ResBody>,
+    F: FnMut(Request<ReqBody>) -> Response<ResBody>,
     ReqBody: Payload,
     ResBody: Payload,
 {
@@ -163,3 +163,24 @@ impl<F, R> fmt::Debug for ServiceFnOk<F, R> {
             .finish()
     }
 }
+
+//#[cfg(test)]
+fn _assert_fn_mut() {
+    fn assert_service<T: Service>(_t: &T) {}
+
+    let mut val = 0;
+
+    let svc = service_fn(move |_req: Request<::Body>| {
+        val += 1;
+        future::ok::<_, Never>(Response::new(::Body::empty()))
+    });
+
+    assert_service(&svc);
+
+    let svc = service_fn_ok(move |_req: Request<::Body>| {
+        val += 1;
+        Response::new(::Body::empty())
+    });
+
+    assert_service(&svc);
+}