diff --git a/src/dc_receive_imf.rs b/src/dc_receive_imf.rs
index 16ddba483..b4cb083f3 100644
--- a/src/dc_receive_imf.rs
+++ b/src/dc_receive_imf.rs
@@ -1623,6 +1623,7 @@ fn dc_create_incoming_rfc724_mid(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::message::Message;
     use crate::test_utils::dummy_context;
 
     #[test]
@@ -1682,4 +1683,38 @@ mod tests {
             Some("123-45-9@stub".into())
         );
     }
+
+    #[test]
+    fn test_is_known_rfc724_mid() {
+        let t = dummy_context();
+        let mut msg = Message::new(Viewtype::Text);
+        msg.text = Some("first message".to_string());
+        let msg_id = chat::add_device_msg(&t.ctx, None, Some(&mut msg)).unwrap();
+        let msg = Message::load_from_db(&t.ctx, msg_id).unwrap();
+
+        // Message-IDs may or may not be surrounded by angle brackets
+        assert!(is_known_rfc724_mid(
+            &t.ctx,
+            format!("<{}>", msg.rfc724_mid).as_str()
+        ));
+        assert!(is_known_rfc724_mid(&t.ctx, &msg.rfc724_mid));
+        assert!(!is_known_rfc724_mid(&t.ctx, "unexistant@message.id"));
+    }
+
+    #[test]
+    fn test_is_msgrmsg_rfc724_mid() {
+        let t = dummy_context();
+        let mut msg = Message::new(Viewtype::Text);
+        msg.text = Some("first message".to_string());
+        let msg_id = chat::add_device_msg(&t.ctx, None, Some(&mut msg)).unwrap();
+        let msg = Message::load_from_db(&t.ctx, msg_id).unwrap();
+
+        // Message-IDs may or may not be surrounded by angle brackets
+        assert!(is_msgrmsg_rfc724_mid(
+            &t.ctx,
+            format!("<{}>", msg.rfc724_mid).as_str()
+        ));
+        assert!(is_msgrmsg_rfc724_mid(&t.ctx, &msg.rfc724_mid));
+        assert!(!is_msgrmsg_rfc724_mid(&t.ctx, "unexistant@message.id"));
+    }
 }