diff --git a/Assets/Cryville/Crtr/Judge.cs b/Assets/Cryville/Crtr/Judge.cs
index bf145a2..c0e3875 100644
--- a/Assets/Cryville/Crtr/Judge.cs
+++ b/Assets/Cryville/Crtr/Judge.cs
@@ -19,13 +19,13 @@ namespace Cryville.Crtr {
 			public JudgeDefinition Definition { get; set; }
 			public ContainerState State { get; set; }
 		}
-		static IComparer<JudgeEvent> _stcmp = new JudgeEventStartTimeComparer();
+		static readonly IComparer<JudgeEvent> _stcmp = new JudgeEventStartTimeComparer();
 		class JudgeEventStartTimeComparer : IComparer<JudgeEvent> {
 			public int Compare(JudgeEvent x, JudgeEvent y) {
 				return x.StartTime.CompareTo(y.StartTime);
 			}
 		}
-		static IComparer<JudgeEvent> _etcmp = new JudgeEventEndTimeComparer();
+		static readonly IComparer<JudgeEvent> _etcmp = new JudgeEventEndTimeComparer();
 		class JudgeEventEndTimeComparer : IComparer<JudgeEvent> {
 			public int Compare(JudgeEvent x, JudgeEvent y) {
 				return x.EndTime.CompareTo(y.EndTime);