diff --git a/README.md b/README.md
index e67ae5b..993780d 100644
--- a/README.md
+++ b/README.md
@@ -90,7 +90,8 @@ For base game characters, it is sufficient to only provide the ID, similar to wh
   _Note_: custom images will only be visible after enabling them in the Grimoire menu!
 - **edition**: the ID of the edition for this character. can be left blank or "custom"
 - **firstNight** / **otherNight**: the position that this character acts on the first / other nights, compared to all
-  other characters
+  other characters<br>
+  _Note_: must be a positive number or zero, with zero being treated as "does not act during the night"
 - **firstNightReminder** / **otherNightReminder**: reminder text for first / other nights
 - **reminders**: reminder tokens, should be an empty array `[]` if none
 - **remindersGlobal**: global reminder tokens that will always be available, no matter if the character is assigned to a player or not
diff --git a/src/store/index.js b/src/store/index.js
index 4ab2cdd..feb528d 100644
--- a/src/store/index.js
+++ b/src/store/index.js
@@ -214,7 +214,7 @@ export default new Vuex.Store({
             state.roles.get(role.id) ||
             Object.assign({}, customRole, role)
         )
-        // default empty icons and placeholders
+        // default empty icons and placeholders, clean up firstNight / otherNight
         .map(role => {
           if (rolesJSONbyId.get(role.id)) return role;
           role.imageAlt = // map team to generic icon
@@ -225,6 +225,8 @@ export default new Vuex.Store({
               demon: "evil",
               fabled: "fabled"
             }[role.team] || "custom";
+          role.firstNight = Math.abs(role.firstNight);
+          role.otherNight = Math.abs(role.otherNight);
           return role;
         })
         // filter out roles that don't match an existing role and also don't have name/ability/team