diff --git a/util/cmake/pro2cmake.py b/util/cmake/pro2cmake.py
index 7eeed440f69..56d7e8d48d0 100755
--- a/util/cmake/pro2cmake.py
+++ b/util/cmake/pro2cmake.py
@@ -28,6 +28,9 @@
 #############################################################################
 
 
+# Requires Python 3.7. The import statement needs to be the first line of code
+# so it's not possible to conditionally check the version and raise an
+# exception.
 from __future__ import annotations
 
 import copy