diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/download/DefaultCacheRepository.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/download/DefaultCacheRepository.java
index 88c3e1bd94..25b8e2a618 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/download/DefaultCacheRepository.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/download/DefaultCacheRepository.java
@@ -181,7 +181,7 @@ public Optional<Path> getLibrary(Library library) {
      */
     public Path cacheLibrary(Library library, Path path, boolean forge) throws IOException {
         String hash = library.getDownload().getSha1();
-        if (hash == null)
+        if (!DigestUtils.isSha1Digest(hash))
             hash = DigestUtils.digestToString(SHA1, path);
 
         Path cache = getFile(SHA1, hash);
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/task/FileDownloadTask.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/task/FileDownloadTask.java
index ecc141a732..2800bab09f 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/task/FileDownloadTask.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/task/FileDownloadTask.java
@@ -246,7 +246,7 @@ public void close() throws IOException {
                         handler.checkIntegrity(temp, file);
                     }
 
-                    if (checksum != null) {
+                    if (checksum != null && !checksum.isEmpty()) {
                         String actualChecksum = HexFormat.of().formatHex(digest.digest());
                         if (!checksum.equalsIgnoreCase(actualChecksum)) {
                             throw new ChecksumMismatchException(algorithm, checksum, actualChecksum);
diff --git a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/CacheRepository.java b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/CacheRepository.java
index 48fbcdc7c7..84e5b689bc 100644
--- a/HMCLCore/src/main/java/org/jackhuang/hmcl/util/CacheRepository.java
+++ b/HMCLCore/src/main/java/org/jackhuang/hmcl/util/CacheRepository.java
@@ -101,7 +101,7 @@ protected Path getFile(String algorithm, String hash) {
     }
 
     protected boolean fileExists(String algorithm, String hash) {
-        if (hash == null) return false;
+        if (!DigestUtils.isSha1Digest(hash)) return false;
         Path file = getFile(algorithm, hash);
         if (Files.exists(file)) {
             try {
@@ -114,13 +114,23 @@ protected boolean fileExists(String algorithm, String hash) {
         }
     }
 
+    private void checkHash(String hash) throws IOException {
+        if (!DigestUtils.isSha1Digest(hash)) {
+            throw new IOException("Not SHA-1 checksum: " + hash);
+        }
+    }
+
     public void tryCacheFile(Path path, String algorithm, String hash) throws IOException {
+        checkHash(hash);
+
         Path cache = getFile(algorithm, hash);
         if (Files.isRegularFile(cache)) return;
         FileUtils.copyFile(path, cache);
     }
 
     public Path cacheFile(Path path, String algorithm, String hash) throws IOException {
+        checkHash(hash);
+
         Path cache = getFile(algorithm, hash);
         FileUtils.copyFile(path, cache);
         return cache;