diff --git a/core/fpdfdoc/cpdf_formfield.h b/core/fpdfdoc/cpdf_formfield.h
index 188477a..945545f 100644
--- a/core/fpdfdoc/cpdf_formfield.h
+++ b/core/fpdfdoc/cpdf_formfield.h
@@ -24,7 +24,7 @@
 class CPDF_Object;
 class CPDF_String;
 
-enum class NotificationOption { kDoNotNotify = 0, kNotify };
+enum class NotificationOption : bool { kDoNotNotify = false, kNotify = true };
 
 enum class FormFieldType : uint8_t {
   kUnknown = 0,