diff --git a/src/unit.rs b/src/unit.rs
index 37530e8..a22ddd9 100644
--- a/src/unit.rs
+++ b/src/unit.rs
@@ -369,7 +369,7 @@ fn send_prelude(unit: &Unit, stream: &mut Stream, redir: bool) -> IoResult<()> {
         }
     }
     if !header::has_header(&unit.headers, "user-agent") {
-        write!(prelude, "User-Agent: ureq\r\n")?;
+        write!(prelude, "User-Agent: ureq/{}\r\n", env!("CARGO_PKG_VERSION"))?;
     }
     if !header::has_header(&unit.headers, "accept") {
         write!(prelude, "Accept: */*\r\n")?;