diff --git a/armsrc/cmac_calc.c b/armsrc/cmac_calc.c
index 9b739eba8..081edae71 100644
--- a/armsrc/cmac_calc.c
+++ b/armsrc/cmac_calc.c
@@ -29,7 +29,7 @@ static ulaes_key_t g_secure_session = {
     .use_schann = false,
 };
 
-// init clears all
+// initialise global secure session object
 void init_secure_session(void) {
     g_secure_session.counter = 0;
     g_secure_session.use_schann = false;