diff --git a/ch03/bb84.py b/ch03/bb84.py
index 5ec07aa..e8e230f 100644
--- a/ch03/bb84.py
+++ b/ch03/bb84.py
@@ -62,7 +62,7 @@ def send_single_bit_with_bb84(
 
     return ((your_message, your_basis), (eve_result, eve_basis))
 
-def simulate_bb84(n_bits: int) -> tuple:
+def simulate_bb84(n_bits: int) -> list:
     your_device = SingleQubitSimulator()
     eve_device = SingleQubitSimulator()