diff --git a/tests/xprop/test.py b/tests/xprop/test.py
index b73b4dae7..e2cddf679 100644
--- a/tests/xprop/test.py
+++ b/tests/xprop/test.py
@@ -270,6 +270,7 @@ if "prepare" in steps:
         print("initial begin", file=tb_file)
 
         for pattern in patterns:
+            # A[0] might be the clock which requires special sequencing
             print(
                 f'    #0; gclk = 1; #0; A[0] = 1\'b{pattern[-1]}; #0; A = {input_width}\'b{pattern}; #5; gclk = 0; $display("%b %b", A, Y); #5',
                 file=tb_file,