diff --git a/install-release.sh b/install-release.sh
index 88364c1..77aa6eb 100644
--- a/install-release.sh
+++ b/install-release.sh
@@ -40,7 +40,7 @@ fi
 # Verification of V2Ray archive
 for LISTSUM in 'md5' 'sha1' 'sha256' 'sha512'; do
     SUM="$(${LISTSUM}sum $ZIP_FILE | sed 's/ .*//')"
-    CHECKSUM="$(grep $(echo $LISTSUM | tr [[:lower:]] [:upper:]) $ZIP_FILE.dgst | sed 's/.* //')"
+    CHECKSUM="$(grep $(echo $LISTSUM | tr [:lower:] [:upper:]) $ZIP_FILE.dgst | sed 's/.* //')"
     if [[ "$SUM" != "$CHECKSUM" ]]; then
         echo 'error: Check failed! Please check your network or try again.'
         exit 1