diff --git a/src/google.rs b/src/google.rs
index a9b30b8..e97e6e4 100644
--- a/src/google.rs
+++ b/src/google.rs
@@ -12,16 +12,34 @@ impl GoogleChatMessage {
         GoogleChatMessage { text: text }
     }
 
+    /// Build a webhook URL with threadKey set to the provided value, and messageReplyOption set to allow threading.
+    pub fn build_webhook_url(webhook_url: &String, thread_key: &String) -> Result<String> {
+        let url = Url::parse(webhook_url)?;
+        // strip any existing threadKey / messageReplyOption parameters
+        let other_params = url
+            .query_pairs()
+            .filter(|(name, _)| name.ne("threadKey") && name.ne("messageReplyOption"));
+        // rebuild URL with the provided threadKey value, and our desired messageReplyOption
+        let mut updated_url = url.clone();
+        updated_url.query_pairs_mut()
+            .clear()
+            .extend_pairs(other_params)
+            .extend_pairs(&[
+                (&"messageReplyOption".to_string(), &"REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD".to_string()),
+                (&"threadKey".to_string(), thread_key)
+            ]);
+        Ok(updated_url.as_str().to_string())
+    }
+
     pub async fn send(
         self,
         webhook_url: &String,
         thread_key: &String,
     ) -> Result<GoogleChatMessage> {
-        let webhook_url = Url::parse_with_params(webhook_url,
-        &[("messageReplyOption", "REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD"), ("threadKey", thread_key)])?;
+        let url = GoogleChatMessage::build_webhook_url(&webhook_url, &thread_key)?;
 
         let response = reqwest::Client::new()
-            .post(webhook_url.as_str())
+            .post(url.to_string())
             .body(serde_json::to_string(&self)?)
             .header("User-Agent", "GU-PR-Bot")
             .send()
@@ -36,3 +54,44 @@ impl GoogleChatMessage {
         ))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_build_threaded_webhook_with_placeholder() {
+        let result = GoogleChatMessage::build_webhook_url(&String::from("https://example.com/ABCDEF?threadKey={threadKey}"), &String::from("1234"));
+        match result {
+            Ok(url) => assert_eq!(url, String::from("https://example.com/ABCDEF?messageReplyOption=REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD&threadKey=1234")),
+            Err(_) => assert!(false),
+        }
+    }
+
+    #[test]
+    fn test_build_threaded_webhook_without_placeholder() {
+        let result = GoogleChatMessage::build_webhook_url(&String::from("https://example.com/ABCDEF"), &String::from("1234"));
+        match result {
+            Ok(url) => assert_eq!(url, String::from("https://example.com/ABCDEF?messageReplyOption=REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD&threadKey=1234")),
+            Err(_) => assert!(false),
+        }
+    }
+
+    #[test]
+    fn test_preserves_other_existing_params() {
+        let result = GoogleChatMessage::build_webhook_url(&String::from("https://example.com/ABCDEF?foo=bar"), &String::from("1234"));
+        match result {
+            Ok(url) => assert_eq!(url, String::from("https://example.com/ABCDEF?foo=bar&messageReplyOption=REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD&threadKey=1234")),
+            Err(_) => assert!(false),
+        }
+    }
+
+    #[test]
+    fn test_overrides_existing_messagereplyoption_parameter() {
+        let result = GoogleChatMessage::build_webhook_url(&String::from("https://example.com/ABCDEF?messageReplyOption=REPLY_MESSAGE"), &String::from("1234"));
+        match result {
+            Ok(url) => assert_eq!(url, String::from("https://example.com/ABCDEF?messageReplyOption=REPLY_MESSAGE_FALLBACK_TO_NEW_THREAD&threadKey=1234")),
+            Err(_) => assert!(false),
+        }
+    }
+}
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