diff --git a/wtransport-proto/src/error.rs b/wtransport-proto/src/error.rs
index 52dc964..4c3612a 100644
--- a/wtransport-proto/src/error.rs
+++ b/wtransport-proto/src/error.rs
@@ -53,6 +53,16 @@ pub enum ErrorCode {
 }
 
 impl ErrorCode {
+    /// Converts this stream [`ErrorCode`] to HTTP/3 error code.
+    /// <https://ietf-wg-webtrans.github.io/draft-ietf-webtrans-http3/draft-ietf-webtrans-http3.html#section-4.3)>
+    pub fn to_http3(self) -> VarInt {
+        let code = self.to_code();
+        let first: u64 = 0x52e4a40fa8db;
+        let code = u64::from(code);
+        let val = first + code + (code / 0x1e);
+        VarInt::try_from_u64(val).expect("Valid conversion")
+    }
+
     /// Returns the integer representation (code) of the error.
     pub fn to_code(self) -> VarInt {
         match self {
diff --git a/wtransport/src/driver/mod.rs b/wtransport/src/driver/mod.rs
index c2987be..6135478 100644
--- a/wtransport/src/driver/mod.rs
+++ b/wtransport/src/driver/mod.rs
@@ -137,7 +137,7 @@ impl Driver {
 
             stream
                 .into_stream()
-                .stop(ErrorCode::BufferedStreamRejected.to_code())
+                .stop(ErrorCode::BufferedStreamRejected.to_http3())
                 .expect("Stream not already stopped");
         }
     }
@@ -164,7 +164,7 @@ impl Driver {
             stream
                 .into_stream()
                 .1
-                .stop(ErrorCode::BufferedStreamRejected.to_code())
+                .stop(ErrorCode::BufferedStreamRejected.to_http3())
                 .expect("Stream not already stopped");
         }
     }
@@ -308,7 +308,7 @@ mod worker {
 
             if let DriverError::Proto(error_code) = &error {
                 self.quic_connection
-                    .close(varint_w2q(error_code.to_code()), b"");
+                    .close(varint_w2q(error_code.to_http3()), b"");
             }
 
             self.driver_result.set(error);
@@ -595,14 +595,14 @@ mod worker {
                         Ok(session_request) => stream.into_session(session_request),
                         Err(HeadersParseError::MethodNotConnect) => {
                             stream
-                                .stop(ErrorCode::RequestRejected.to_code())
+                                .stop(ErrorCode::RequestRejected.to_http3())
                                 .expect("Stream not already stopped");
                             return Ok(());
                         }
                         // TODO(biagio): we might have more granularity with errors
                         Err(_) => {
                             stream
-                                .stop(ErrorCode::Message.to_code())
+                                .stop(ErrorCode::Message.to_http3())
                                 .expect("Stream not already stopped");
                             return Ok(());
                         }
@@ -613,7 +613,7 @@ mod worker {
                         Err(TrySendError::Full(mut stream)) => {
                             debug!("Discarding session request: sessions queue is full");
                             stream
-                                .stop(ErrorCode::RequestRejected.to_code())
+                                .stop(ErrorCode::RequestRejected.to_http3())
                                 .expect("Stream not already stopped");
                         }
                         Err(TrySendError::Closed(_)) => return Err(DriverError::NotConnected),
diff --git a/wtransport/src/endpoint.rs b/wtransport/src/endpoint.rs
index 1b270db..aee3ce6 100644
--- a/wtransport/src/endpoint.rs
+++ b/wtransport/src/endpoint.rs
@@ -387,7 +387,7 @@ impl Endpoint<endpoint_side::Client> {
             let frame = match stream_session.read_frame().await {
                 Ok(frame) => frame,
                 Err(ProtoReadError::H3(error_code)) => {
-                    quic_connection.close(varint_w2q(error_code.to_code()), b"");
+                    quic_connection.close(varint_w2q(error_code.to_http3()), b"");
                     return Err(ConnectingError::ConnectionError(
                         ConnectionError::local_h3_error(error_code),
                     ));
@@ -404,7 +404,7 @@ impl Endpoint<endpoint_side::Client> {
         };
 
         if !matches!(frame.kind(), FrameKind::Headers) {
-            quic_connection.close(varint_w2q(ErrorCode::FrameUnexpected.to_code()), b"");
+            quic_connection.close(varint_w2q(ErrorCode::FrameUnexpected.to_http3()), b"");
             return Err(ConnectingError::ConnectionError(
                 ConnectionError::local_h3_error(ErrorCode::FrameUnexpected),
             ));
@@ -413,7 +413,7 @@ impl Endpoint<endpoint_side::Client> {
         let headers = match Headers::with_frame(&frame) {
             Ok(headers) => headers,
             Err(error_code) => {
-                quic_connection.close(varint_w2q(error_code.to_code()), b"");
+                quic_connection.close(varint_w2q(error_code.to_http3()), b"");
                 return Err(ConnectingError::ConnectionError(
                     ConnectionError::local_h3_error(error_code),
                 ));
@@ -423,7 +423,7 @@ impl Endpoint<endpoint_side::Client> {
         let session_response = match SessionResponseProto::try_from(headers) {
             Ok(session_response) => session_response,
             Err(_) => {
-                quic_connection.close(varint_w2q(ErrorCode::Message.to_code()), b"");
+                quic_connection.close(varint_w2q(ErrorCode::Message.to_http3()), b"");
                 return Err(ConnectingError::ConnectionError(
                     ConnectionError::local_h3_error(ErrorCode::Message),
                 ));
@@ -759,7 +759,7 @@ impl SessionRequest {
             }
             Err(ProtoWriteError::Stopped) => {
                 self.quic_connection
-                    .close(varint_w2q(ErrorCode::ClosedCriticalStream.to_code()), b"");
+                    .close(varint_w2q(ErrorCode::ClosedCriticalStream.to_http3()), b"");
 
                 Err(ConnectionError::local_h3_error(
                     ErrorCode::ClosedCriticalStream,