diff --git a/lib/src/transport.rs b/lib/src/transport.rs
index 7c13d54..98690e4 100644
--- a/lib/src/transport.rs
+++ b/lib/src/transport.rs
@@ -32,11 +32,12 @@ impl Transport {
             Box::new(std::io::Error::new(std::io::ErrorKind::InvalidInput, "Invalid endpoint")) as Box<dyn std::error::Error>
         })?;
 
-        let mut request_builder = self.client.request(method, url).header(
-            reqwest::header::USER_AGENT,
-            self.config.user_agent.clone().unwrap_or_default(),
-        );
+        let mut request_builder = self.client.request(method, url);
 
+        if let Some(ref user_agent) = self.config.user_agent {
+            request_builder = request_builder.header(reqwest::header::USER_AGENT, user_agent.clone());
+        }
+        
         if let Some(ref params_value) = params {
             // Validate or log params_value before setting it as query parameters
             if params_value.is_object() {