diff --git a/Program.cs b/Program.cs
index 3dbc5b8..ba30395 100644
--- a/Program.cs
+++ b/Program.cs
@@ -104,7 +104,7 @@ 4. 编解码失败
 		}
 	}
 
-	FileInfo input, output;
+	FileInfo? input = null, output = null;
 
 	// foreach files in the list
 	foreach (var file in args[1].Split(',')) {
@@ -149,9 +149,9 @@ 4. 编解码失败
 			}
 		}
 
-		FileInfo output;
-		DirectoryInfo outputParentDirectoryInfo;
-		string relativePath, relativeDirectory;
+		FileInfo? output = null;
+		DirectoryInfo? outputParentDirectoryInfo = null;
+		string? relativePath = null, relativeDirectory = null;
 
 		// foreach files in the list
 		foreach (var input in inputDirectoryInfo.EnumerateFiles("*", SearchOption.AllDirectories)) {