diff --git a/src/zulip/api.rs b/src/zulip/api.rs
index 0c53c6e..9e31923 100644
--- a/src/zulip/api.rs
+++ b/src/zulip/api.rs
@@ -126,6 +126,21 @@ impl ZulipApi {
         Ok(response)
     }
 
+    /// Is a Zulip stream private?
+    pub(crate) fn is_stream_private(&self, stream_id: u64) -> anyhow::Result<bool> {
+        #[derive(Deserialize)]
+        struct OneZulipStream {
+            stream: ZulipStream,
+        }
+
+        Ok(self
+            .req(reqwest::Method::GET, &format!("/streams/{stream_id}"), None)?
+            .error_for_status()?
+            .json::<OneZulipStream>()?
+            .stream
+            .invite_only)
+    }
+
     pub(crate) fn update_user_group_members(
         &self,
         user_group_id: u64,
@@ -224,13 +239,19 @@ impl ZulipApi {
             Ok(())
         };
 
-        let subscriptions = format!("{{\"name\": \"{stream_name}\", \"description\": \"\"}}");
-        let add_ids = serialize_as_array(add_ids);
-        submit(reqwest::Method::POST, subscriptions, add_ids)?;
+        if !add_ids.is_empty() {
+            let subscriptions = format!("{{\"name\": \"{stream_name}\", \"description\": \"\"}}");
+            let add_ids = serialize_as_array(add_ids);
+            submit(reqwest::Method::POST, subscriptions, add_ids)?;
+        }
 
-        let subscriptions = format!("[{stream_name}]");
-        let remove_ids = serialize_as_array(remove_ids);
-        submit(reqwest::Method::DELETE, subscriptions, remove_ids)
+        if !remove_ids.is_empty() {
+            let subscriptions = format!("[{stream_name}]");
+            let remove_ids = serialize_as_array(remove_ids);
+            submit(reqwest::Method::DELETE, subscriptions, remove_ids)?;
+        }
+
+        Ok(())
     }
 
     /// Perform a request against the Zulip API
@@ -302,6 +323,7 @@ struct ZulipStreams {
 pub(crate) struct ZulipStream {
     pub(crate) stream_id: u64,
     pub(crate) name: String,
+    pub(crate) invite_only: bool,
 }
 
 /// Membership of a Zulip stream
diff --git a/src/zulip/mod.rs b/src/zulip/mod.rs
index 41b93e2..77066f6 100644
--- a/src/zulip/mod.rs
+++ b/src/zulip/mod.rs
@@ -126,6 +126,7 @@ impl SyncZulip {
                 ));
             }
         };
+        let is_stream_private = self.zulip_controller.is_stream_private(stream_id)?;
 
         let existing_members = self.zulip_controller.stream_members_from_id(stream_id)?;
         log::debug!(
@@ -136,11 +137,15 @@ impl SyncZulip {
             .filter(|i| !existing_members.contains(i))
             .copied()
             .collect::<Vec<_>>();
-        let remove_ids = existing_members
-            .iter()
-            .filter(|i| !member_ids.contains(i))
-            .copied()
-            .collect::<Vec<_>>();
+        let remove_ids = if is_stream_private {
+            existing_members
+                .iter()
+                .filter(|i| !member_ids.contains(i))
+                .copied()
+                .collect::<Vec<_>>()
+        } else {
+            vec![]
+        };
         if add_ids.is_empty() && remove_ids.is_empty() {
             log::debug!("'{stream_name}' stream ({stream_id}) does not need to be updated");
             Ok(None)
@@ -463,4 +468,8 @@ impl ZulipController {
     fn stream_members_from_id(&self, stream_id: u64) -> anyhow::Result<Vec<u64>> {
         self.zulip_api.get_stream_members(stream_id)
     }
+
+    fn is_stream_private(&self, stream_id: u64) -> anyhow::Result<bool> {
+        self.zulip_api.is_stream_private(stream_id)
+    }
 }