diff --git a/server/src/main/java/cn/keking/utils/KkFileUtils.java b/server/src/main/java/cn/keking/utils/KkFileUtils.java
index 16b0db31..80489813 100644
--- a/server/src/main/java/cn/keking/utils/KkFileUtils.java
+++ b/server/src/main/java/cn/keking/utils/KkFileUtils.java
@@ -93,7 +93,7 @@ public class KkFileUtils {
      * @return 文件后缀
      */
     public static String suffixFromFileName(String fileName) {
-        return fileName.substring(fileName.lastIndexOf(".") + 1);
+        return fileName.substring(fileName.lastIndexOf(".") + 1).toLowerCase();
     }