diff --git a/src/core/utils/stream/try_ready.rs b/src/core/utils/stream/try_ready.rs
index feb380675..3fbcbc454 100644
--- a/src/core/utils/stream/try_ready.rs
+++ b/src/core/utils/stream/try_ready.rs
@@ -24,7 +24,7 @@ fn ready_try_for_each<F>(
 		self, f: F,
 	) -> TryForEach<Self, Ready<Result<(), E>>, impl FnMut(S::Ok) -> Ready<Result<(), E>>>
 	where
-		F: Fn(S::Ok) -> Result<(), E>;
+		F: FnMut(S::Ok) -> Result<(), E>;
 }
 
 impl<T, E, S> TryReadyExt<T, E, S> for S
@@ -42,10 +42,10 @@ fn ready_and_then<U, F>(self, f: F) -> AndThen<Self, Ready<Result<U, E>>, impl F
 
 	#[inline]
 	fn ready_try_for_each<F>(
-		self, f: F,
+		self, mut f: F,
 	) -> TryForEach<Self, Ready<Result<(), E>>, impl FnMut(S::Ok) -> Ready<Result<(), E>>>
 	where
-		F: Fn(S::Ok) -> Result<(), E>,
+		F: FnMut(S::Ok) -> Result<(), E>,
 	{
 		self.try_for_each(move |t| ready(f(t)))
 	}