diff --git a/crates/ruma-appservice-api/CHANGELOG.md b/crates/ruma-appservice-api/CHANGELOG.md
index 6770dbbe..0addc5d9 100644
--- a/crates/ruma-appservice-api/CHANGELOG.md
+++ b/crates/ruma-appservice-api/CHANGELOG.md
@@ -1,5 +1,10 @@
 # [unreleased]
 
+Breaking changes:
+
+* The `url` field of `Registration` is now an `Option<String>`. This should have
+  always been the case.
+
 # 0.9.0
 
 Improvements:
diff --git a/crates/ruma-appservice-api/src/lib.rs b/crates/ruma-appservice-api/src/lib.rs
index f6f74d11..25af421d 100644
--- a/crates/ruma-appservice-api/src/lib.rs
+++ b/crates/ruma-appservice-api/src/lib.rs
@@ -74,7 +74,9 @@ pub struct Registration {
     pub id: String,
 
     /// The URL for the application service.
-    pub url: String,
+    ///
+    /// Optionally set to `null` if no traffic is required.
+    pub url: Option<String>,
 
     /// A unique token for application services to use to authenticate requests to Homeservers.
     pub as_token: String,
@@ -112,7 +114,9 @@ pub struct RegistrationInit {
     pub id: String,
 
     /// The URL for the application service.
-    pub url: String,
+    ///
+    /// Optionally set to `null` if no traffic is required.
+    pub url: Option<String>,
 
     /// A unique token for application services to use to authenticate requests to Homeservers.
     pub as_token: String,
diff --git a/crates/ruma-appservice-api/tests/appservice_registration.rs b/crates/ruma-appservice-api/tests/appservice_registration.rs
index 38dfd3f2..6499bada 100644
--- a/crates/ruma-appservice-api/tests/appservice_registration.rs
+++ b/crates/ruma-appservice-api/tests/appservice_registration.rs
@@ -21,7 +21,7 @@ fn registration_deserialization() {
     let observed: Registration = serde_yaml::from_str(registration_config).unwrap();
 
     assert_eq!(observed.id, "IRC Bridge");
-    assert_eq!(observed.url, "http://127.0.0.1:1234");
+    assert_eq!(observed.url.unwrap(), "http://127.0.0.1:1234");
     assert_eq!(
         observed.as_token,
         "30c05ae90a248a4188e620216fa72e349803310ec83e2a77b34fe90be6081f46"
@@ -59,5 +59,5 @@ fn config_with_optional_url() {
           rooms: []
         "#;
     assert_matches!(serde_yaml::from_str(registration_config).unwrap(), Registration { url, .. });
-    assert_eq!(url, "null");
+    assert_eq!(url, None);
 }