diff --git a/src/client.rs b/src/client.rs
index e94706c..206ac0d 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -60,7 +60,7 @@ impl Client {
         priority: Priority,
         cancellable: Cancellable,
         certificate: Option<TlsCertificate>,
-        callback: impl Fn(Result<Response, Error>) + 'static,
+        callback: impl FnOnce(Result<Response, Error>) + 'static,
     ) {
         // Begin new connection
         // * [NetworkAddress](https://docs.gtk.org/gio/class.NetworkAddress.html) required for valid
diff --git a/src/client/connection.rs b/src/client/connection.rs
index 380a115..66a745c 100644
--- a/src/client/connection.rs
+++ b/src/client/connection.rs
@@ -56,7 +56,7 @@ impl Connection {
         request: Request,
         priority: Priority,
         cancellable: Cancellable,
-        callback: impl Fn(Result<Response, Error>) + 'static,
+        callback: impl FnOnce(Result<Response, Error>) + 'static,
     ) {
         match request {
             Request::Gemini(request) => {
@@ -77,7 +77,7 @@ impl Connection {
         request: Gemini,
         priority: Priority,
         cancellable: Cancellable,
-        callback: impl Fn(Result<Response, Error>) + 'static,
+        callback: impl FnOnce(Result<Response, Error>) + 'static,
     ) {
         self.bytes_request_async(&request.to_bytes(), priority, cancellable, callback);
     }
@@ -91,7 +91,7 @@ impl Connection {
         request: Titan,
         priority: Priority,
         cancellable: Cancellable,
-        callback: impl Fn(Result<Response, Error>) + 'static,
+        callback: impl FnOnce(Result<Response, Error>) + 'static,
     ) {
         self.bytes_request_async(&request.to_bytes(), priority, cancellable, callback);
     }
@@ -107,7 +107,7 @@ impl Connection {
         request: &Bytes,
         priority: Priority,
         cancellable: Cancellable,
-        callback: impl Fn(Result<Response, Error>) + 'static,
+        callback: impl FnOnce(Result<Response, Error>) + 'static,
     ) {
         self.stream().output_stream().write_bytes_async(
             request,