diff --git a/actix-http/src/cookie/builder.rs b/actix-http/src/cookie/builder.rs
index 383c31b1c..c3820abf0 100644
--- a/actix-http/src/cookie/builder.rs
+++ b/actix-http/src/cookie/builder.rs
@@ -107,7 +107,9 @@ impl CookieBuilder {
     /// ```
     #[inline]
     pub fn max_age_time(mut self, value: Duration) -> CookieBuilder {
-        self.cookie.set_max_age(value);
+        // Truncate any nanoseconds from the Duration, as they aren't represented within `Max-Age`
+        // and would cause two otherwise identical `Cookie` instances to not be equivalent to one another.
+        self.cookie.set_max_age(Duration::seconds(value.whole_seconds()));
         self
     }