diff --git a/src/Calendar.tsx b/src/Calendar.tsx
index 9bb37899..c736ebce 100644
--- a/src/Calendar.tsx
+++ b/src/Calendar.tsx
@@ -843,7 +843,7 @@ Calendar.propTypes = {
   minDate: isMinDate,
   minDetail: PropTypes.oneOf(allViews),
   navigationAriaLabel: PropTypes.string,
-  navigationAriaLive: PropTypes.oneOf(['off', 'polite', 'assertive']),
+  navigationAriaLive: PropTypes.oneOf(['off', 'polite', 'assertive'] as const),
   navigationLabel: PropTypes.func,
   next2AriaLabel: PropTypes.string,
   next2Label: PropTypes.node,
@@ -863,7 +863,7 @@ Calendar.propTypes = {
   prev2Label: PropTypes.node,
   prevAriaLabel: PropTypes.string,
   prevLabel: PropTypes.node,
-  returnValue: PropTypes.oneOf(['start', 'end', 'range']),
+  returnValue: PropTypes.oneOf(['start', 'end', 'range'] as const),
   selectRange: PropTypes.bool,
   showDoubleView: PropTypes.bool,
   showFixedNumberOfWeeks: PropTypes.bool,
diff --git a/src/shared/propTypes.ts b/src/shared/propTypes.ts
index c37a8f7b..33a04cc0 100644
--- a/src/shared/propTypes.ts
+++ b/src/shared/propTypes.ts
@@ -9,7 +9,10 @@ const calendarTypes = Object.values(CALENDAR_TYPES);
 const deprecatedCalendarTypes = Object.values(DEPRECATED_CALENDAR_TYPES);
 const allViews = ['century', 'decade', 'year', 'month'];
 
-export const isCalendarType = PropTypes.oneOf([...calendarTypes, ...deprecatedCalendarTypes]);
+export const isCalendarType = PropTypes.oneOf([
+  ...calendarTypes,
+  ...deprecatedCalendarTypes,
+] as const);
 
 export const isClassName = PropTypes.oneOfType([
   PropTypes.string,