diff --git a/setup.py b/setup.py
index a67042b..e4aeb7d 100644
--- a/setup.py
+++ b/setup.py
@@ -32,6 +32,7 @@
         "openfermion>=1.5.1",
         "pennylane>=0.29.1",
         "scipy>=1.5.2",
+        # Sympy 1.13 produces different results for Simon's algorithm
         "sympy<1.13",
     ],
     extras_require={