diff --git a/src/lib.rs b/src/lib.rs
index 36e9ac2..29b308f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -366,10 +366,16 @@ impl Account {
 
     /// Revokes a previously issued certificate
     pub async fn revoke<'a>(&'a self, payload: &RevocationRequest<'a>) -> Result<(), Error> {
-        let rsp = self
-            .inner
-            .post(Some(payload), None, &self.inner.client.urls.revoke_cert)
-            .await?;
+        let revoke_url = match self.inner.client.urls.revoke_cert.as_deref() {
+            Some(url) => url,
+            // This happens because the current account credentials were deserialized from an
+            // older version which only serialized a subset of the directory URLs. You should
+            // make sure the account credentials include a `directory` field containing a
+            // string with the server's directory URL.
+            None => return Err("no revokeCert URL found".into()),
+        };
+
+        let rsp = self.inner.post(Some(payload), None, revoke_url).await?;
         // The body is empty if the request was successful
         let _ = Problem::from_response(rsp).await?;
         Ok(())
diff --git a/src/types.rs b/src/types.rs
index 1cd26d3..dfd73dd 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -60,6 +60,9 @@ pub struct AccountCredentials {
     #[serde(with = "pkcs8_serde")]
     pub(crate) key_pkcs8: Vec<u8>,
     pub(crate) directory: Option<String>,
+    /// We never serialize `urls` by default, but we support deserializing them
+    /// in order to support serialized data from older versions of the library.
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub(crate) urls: Option<DirectoryUrls>,
 }
 
@@ -359,7 +362,12 @@ pub(crate) struct DirectoryUrls {
     pub(crate) new_nonce: String,
     pub(crate) new_account: String,
     pub(crate) new_order: String,
-    pub(crate) revoke_cert: String,
+    // The fields below were added later and old `AccountCredentials` may not have it.
+    // Newer deserialized account credentials grab a fresh set of `DirectoryUrls` on
+    // deserialization, so they should be fine. Newer fields should be optional, too.
+    pub(crate) new_authz: Option<String>,
+    pub(crate) revoke_cert: Option<String>,
+    pub(crate) key_change: Option<String>,
 }
 
 #[derive(Serialize)]