diff --git a/Assets/Cryville/Common/Pdt/PdtInterpreter.cs b/Assets/Cryville/Common/Pdt/PdtInterpreter.cs
index c405f33..d15754d 100644
--- a/Assets/Cryville/Common/Pdt/PdtInterpreter.cs
+++ b/Assets/Cryville/Common/Pdt/PdtInterpreter.cs
@@ -1,10 +1,10 @@
 using Cryville.Common.Collections;
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
 using System.Text.RegularExpressions;
+using CMath = System.Math;
 
 namespace Cryville.Common.Pdt {
 	/// <summary>
@@ -302,13 +302,13 @@ namespace Cryville.Common.Pdt {
 			int pos = interpreter.Position;
 			if (pos >= src.Length) return "Failed to interpret the PDT: There are some missing or redundant tokens";
 			int lineStartPos = src.LastIndexOf('\n', pos) + 1;
-			int previewStartPos = src.LastIndexOf('\n', pos, 64);
+			int previewStartPos = src.LastIndexOf('\n', pos, CMath.Min(64, pos));
 			if (previewStartPos == -1) {
 				previewStartPos = pos - 64;
 				if (previewStartPos < 0) previewStartPos = 0;
 			}
 			else previewStartPos++;
-			int previewEndPos = src.IndexOf('\n', pos, 64);
+			int previewEndPos = src.IndexOf('\n', pos, CMath.Min(64, src.Length - pos));
 			if (previewEndPos == -1) {
 				previewEndPos = pos + 64;
 				if (previewEndPos > src.Length) previewEndPos = src.Length;