diff --git a/reqwest-tracing/src/reqwest_otel_span_macro.rs b/reqwest-tracing/src/reqwest_otel_span_macro.rs
index 3f3d732..b60a7fb 100644
--- a/reqwest-tracing/src/reqwest_otel_span_macro.rs
+++ b/reqwest-tracing/src/reqwest_otel_span_macro.rs
@@ -125,7 +125,7 @@ macro_rules! reqwest_otel_span {
             let host_port = url.port_or_known_default().unwrap_or(0) as i64;
             let otel_name = $name.to_string();
             let header_default = &::http::HeaderValue::from_static("");
-            let user_agent = format!("{:?}", $request.headers().get("user_agent").unwrap_or(header_default)).replace('"', "");
+            let user_agent = format!("{:?}", $request.headers().get("user-agent").unwrap_or(header_default)).replace('"', "");
 
             macro_rules! request_span {
                 ($lvl:expr) => {