diff --git a/tests/pcl.lisp b/tests/pcl.lisp
index 218fead8739a6d8fe1ea0534091027c7a17a4802..c49e279d7e0636a60e41da7d1aac1d7beb2a0458 100644
--- a/tests/pcl.lisp
+++ b/tests/pcl.lisp
@@ -1,3 +1,7 @@
+;;; Tests for PCL, taken from src/pcl/rt.
+;;;
+;;; It's clear that the tests used mk defsystem to load the tests, but
+;;; it's not clear if the tests were compiled or not before running.
 
 (defpackage "PCL-TESTS"
   (:use "COMMON-LISP" "PCL" "LISP-UNIT"))