diff --git a/src/proto/streams/flow_control.rs b/src/proto/streams/flow_control.rs
index 521be38..fef8b47 100644
--- a/src/proto/streams/flow_control.rs
+++ b/src/proto/streams/flow_control.rs
@@ -48,7 +48,7 @@ impl FlowControl {
     }
 
     pub fn assign_capacity(&mut self, capacity: WindowSize) {
-        self.available + capacity;
+        self.available += capacity;
     }
 
     /// Returns the number of bytes available but not assigned to the window.
diff --git a/tests/prioritization.rs b/tests/prioritization.rs
index bc71834..d6fd1c9 100644
--- a/tests/prioritization.rs
+++ b/tests/prioritization.rs
@@ -35,7 +35,7 @@ fn single_stream_send_large_body() {
     let mut stream = h2.request(request, false).unwrap();
 
     // Reserve capacity to send the payload
-    stream.reserve_capacity(payload.len()).unwrap();
+    stream.reserve_capacity(payload.len());
 
     // The capacity should be immediately allocated
     assert_eq!(stream.capacity(), payload.len());
@@ -88,7 +88,7 @@ fn single_stream_send_extra_large_body_multi_frames_one_buffer() {
 
     let mut stream = h2.request(request, false).unwrap();
 
-    stream.reserve_capacity(payload.len()).unwrap();
+    stream.reserve_capacity(payload.len());
 
     // The capacity should be immediately allocated
     assert_eq!(stream.capacity(), payload.len());
@@ -153,7 +153,7 @@ fn single_stream_send_extra_large_body_multi_frames_multi_buffer() {
 
     let mut stream = h2.request(request, false).unwrap();
 
-    stream.reserve_capacity(payload.len()).unwrap();
+    stream.reserve_capacity(payload.len());
 
     // The capacity should be immediately allocated
     assert_eq!(stream.capacity(), payload.len());
diff --git a/tests/stream_states.rs b/tests/stream_states.rs
index ef37652..a5b2520 100644
--- a/tests/stream_states.rs
+++ b/tests/stream_states.rs
@@ -75,7 +75,7 @@ fn send_recv_data() {
     let mut stream = h2.request(request, false).unwrap();
 
     // Reserve send capacity
-    stream.reserve_capacity(5).unwrap();
+    stream.reserve_capacity(5);
 
     assert_eq!(stream.capacity(), 5);