diff --git a/crates/handlers/src/oauth2/introspection.rs b/crates/handlers/src/oauth2/introspection.rs
index f67676720..608871e54 100644
--- a/crates/handlers/src/oauth2/introspection.rs
+++ b/crates/handlers/src/oauth2/introspection.rs
@@ -284,7 +284,7 @@ pub(crate) async fn post(
                 exp: access_token.expires_at,
                 expires_in: access_token
                     .expires_at
-                    .map(|expires_at| expires_at.signed_duration_since(clock.now()).num_seconds()),
+                    .map(|expires_at| expires_at.signed_duration_since(clock.now())),
                 iat: Some(access_token.created_at),
                 nbf: Some(access_token.created_at),
                 sub,
@@ -421,7 +421,7 @@ pub(crate) async fn post(
                 exp: access_token.expires_at,
                 expires_in: access_token
                     .expires_at
-                    .map(|expires_at| expires_at.signed_duration_since(clock.now()).num_seconds()),
+                    .map(|expires_at| expires_at.signed_duration_since(clock.now())),
                 iat: Some(access_token.created_at),
                 nbf: Some(access_token.created_at),
                 sub: Some(user.sub),
diff --git a/crates/oauth2-types/src/requests.rs b/crates/oauth2-types/src/requests.rs
index a4246e9b4..631b33309 100644
--- a/crates/oauth2-types/src/requests.rs
+++ b/crates/oauth2-types/src/requests.rs
@@ -769,7 +769,8 @@ pub struct IntrospectionResponse {
 
     /// Relative timestamp indicating when the token will expire,
     /// in seconds from the current instant.
-    pub expires_in: Option<i64>,
+    #[serde_as(as = "Option<DurationSeconds<i64>>")]
+    pub expires_in: Option<Duration>,
 
     /// Timestamp indicating when the token was issued.
     #[serde_as(as = "Option<TimestampSeconds>")]