diff --git a/ethexe/malachite/core/src/streaming.rs b/ethexe/malachite/core/src/streaming.rs
index 7f9d3c37778..74f6d92b012 100644
--- a/ethexe/malachite/core/src/streaming.rs
+++ b/ethexe/malachite/core/src/streaming.rs
@@ -98,7 +98,7 @@ impl StreamState {
         }
         if msg.is_fin() {
             self.fin_received = true;
-            self.total_messages = msg.sequence as usize + 1;
+            self.total_messages = (msg.sequence as usize).saturating_add(1);
         }
         self.buffer.push(msg);
         if self.is_done() {
@@ -352,4 +352,12 @@ mod tests {
             map.streams.len(),
         );
     }
+
+    #[test]
+    fn fin_at_u64_max_sequence_does_not_panic() {
+        let mut map = PartStreamsMap::new();
+        let p = peer_id(13);
+        let s = sid(0xDEADBEEF);
+        let _ = map.insert(p, fin_msg(s, u64::MAX));
+    }
 }