diff --git a/ethexe/runtime/common/tests/auto_tester_b64c5073de45.rs b/ethexe/runtime/common/tests/auto_tester_b64c5073de45.rs
new file mode 100644
index 00000000000..28c70ddda81
--- /dev/null
+++ b/ethexe/runtime/common/tests/auto_tester_b64c5073de45.rs
@@ -0,0 +1,41 @@
+// scenario: duplicate_key
+// param_signature: Waitlist::wait twice with same dispatch.id triggers debug_assert failure
+// hash: b64c5073de45
+
+use ethexe_runtime_common::state::{Waitlist, Dispatch, PayloadLookup};
+use ethexe_common::gear::MessageType;
+use gprimitives::{ActorId, MessageId};
+use gear_core::buffer::Payload;
+use gear_core_errors::SuccessReplyReason;
+
+#[test]
+fn test_waitlist_wait_duplicate_id_debug_assert() {
+    let mut waitlist = Waitlist::default();
+
+    let dispatch = Dispatch::reply(
+        MessageId::from(42),
+        ActorId::from(1),
+        PayloadLookup::Direct(Payload::new()),
+        0,
+        SuccessReplyReason::Auto,
+        MessageType::Canonical,
+        false,
+    );
+
+    // First wait — succeeds
+    waitlist.wait(dispatch.clone(), 100);
+
+    // Second wait with same id — debug_assert!(r.is_none()) fires in debug builds.
+    // In release builds, the insert silently overwrites the previous entry.
+    // Either way the behavior needs to be consistent: the key is deduplicated.
+    waitlist.wait(dispatch.clone(), 200);
+
+    // Check how many entries we have: should be 1 (second overwrote first) in release,
+    // or this panics in debug due to debug_assert.
+    let inner = waitlist.into_inner();
+    assert_eq!(inner.len(), 1, "duplicate id should only have one entry");
+
+    // The surviving entry should have expiry=200 (last write wins)
+    let entry = inner.get(&MessageId::from(42)).expect("entry must exist");
+    assert_eq!(entry.expiry, 200, "last write should win");
+}