diff --git a/lib/sympto/cervix.js b/lib/sympto/cervix.js
index 15c990a2260c4d1dcaaebd5b780aba266894b1ac..e09205c10c58b22d06087dbc71e35d095898a6dd 100644
--- a/lib/sympto/cervix.js
+++ b/lib/sympto/cervix.js
@@ -7,6 +7,7 @@ export default function (cycleDays, tempEvalEndIndex) {
   // we search for the day of cervix peak, which must:
   // * have fertile cervix values
   // * be followed by at least 3 days
+  // * must happen prior to end of temperature evaluation
   // these 3 following days must all show infertile cervix values
   // if everything applies we must check the days until the end of temperature evaluation
   // during these relevantDays no fertile cervix must occur