diff --git a/crates/sdp-types/src/media_description.rs b/crates/sdp-types/src/media_description.rs
index 861db97..ec84403 100644
--- a/crates/sdp-types/src/media_description.rs
+++ b/crates/sdp-types/src/media_description.rs
@@ -141,7 +141,7 @@ impl fmt::Display for MediaDescription {
         }
 
         if let Some(setup) = self.setup {
-            write!(f, "a={setup}\r\n")?;
+            write!(f, "a=setup:{setup}\r\n")?;
         }
 
         for fingerprint in &self.fingerprint {
diff --git a/crates/sdp-types/src/session_description.rs b/crates/sdp-types/src/session_description.rs
index 5484456..c9ae952 100644
--- a/crates/sdp-types/src/session_description.rs
+++ b/crates/sdp-types/src/session_description.rs
@@ -130,7 +130,7 @@ impl fmt::Display for SessionDescription {
         }
 
         if let Some(setup) = self.setup {
-            write!(f, "a={setup}\r\n")?;
+            write!(f, "a=setup:{setup}\r\n")?;
         }
 
         for fingerprint in &self.fingerprint {