diff --git a/core/src/upgrade/transfer.rs b/core/src/upgrade/transfer.rs
index 6ea678a2..5bc6d5a8 100644
--- a/core/src/upgrade/transfer.rs
+++ b/core/src/upgrade/transfer.rs
@@ -219,6 +219,7 @@ where
                                 len_buf,
                                 max_size,
                             };
+                            return Ok(Async::NotReady);
                         }
                     }
                 }
@@ -229,6 +230,7 @@ where
                         }
                         Async::NotReady => {
                             self.inner = ReadOneInner::ReadRest(inner);
+                            return Ok(Async::NotReady);
                         }
                     }
                 }
@@ -376,6 +378,7 @@ where
                         }
                         Async::NotReady => {
                             self.inner = RequestResponseInner::Write(inner, max_size, then);
+                            return Ok(Async::NotReady);
                         }
                     }
                 }
@@ -383,6 +386,7 @@ where
                     Async::Ready(packet) => return Ok(Async::Ready(packet)),
                     Async::NotReady => {
                         self.inner = RequestResponseInner::Read(inner);
+                        return Ok(Async::NotReady);
                     }
                 },
                 RequestResponseInner::Poisoned => panic!(),