diff --git a/OpenUtau.Core/Classic/Flags/UstFlag.cs b/OpenUtau.Core/Classic/Flags/UstFlag.cs
index 81948ecab..7af74c5d4 100644
--- a/OpenUtau.Core/Classic/Flags/UstFlag.cs
+++ b/OpenUtau.Core/Classic/Flags/UstFlag.cs
@@ -10,5 +10,9 @@ public UstFlag(string key, int value) {
             Key = key ?? throw new ArgumentNullException(nameof(key));
             Value = value;
         }
+
+        public override string ToString() {
+            return Key + Value;
+        }
     }
 }
diff --git a/OpenUtau.Core/Classic/Flags/UstFlagParser.cs b/OpenUtau.Core/Classic/Flags/UstFlagParser.cs
index 2dfed5be8..e6ce4cc6a 100644
--- a/OpenUtau.Core/Classic/Flags/UstFlagParser.cs
+++ b/OpenUtau.Core/Classic/Flags/UstFlagParser.cs
@@ -1,17 +1,18 @@
-
-using System;
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Text;
 
 namespace OpenUtau.Classic.Flags {
     public class UstFlagParser {
         public IList<UstFlag> Parse(string text) {
             List<UstFlag> flags = new List<UstFlag>();
+            if (string.IsNullOrEmpty(text)) return flags;
+
             var keyBuilder = new StringBuilder();
             var valueBuilder = new StringBuilder();
             bool wasDigit = false;
+
             for (int i = 0; i <= text.Length; ++i) {
-                if (i == text.Length || char.IsLetter(text[i]) && wasDigit) {
+                if (i == text.Length || (char.IsLetter(text[i]) || text[i] == '/') && wasDigit) {
                     string key = keyBuilder.ToString();
                     if (!int.TryParse(valueBuilder.ToString(), out int value)) {
                         value = 0;
@@ -29,7 +30,7 @@ public IList<UstFlag> Parse(string text) {
                 if (c == '-' || c == '+' || char.IsDigit(c)) {
                     valueBuilder.Append(c);
                     wasDigit = true;
-                } else if (char.IsLetter(c)) {
+                } else if (char.IsLetter(c) || c == '/') {
                     if (keyBuilder.Length == 0 && IsSingleCharacterFlag(c)) {
                         flags.Add(new UstFlag(c.ToString(), 0));
                         continue;
diff --git a/OpenUtau.Test/Classic/Flags/UstFlagParserTest.cs b/OpenUtau.Test/Classic/Flags/UstFlagParserTest.cs
index a5cf9d200..37d3467e9 100644
--- a/OpenUtau.Test/Classic/Flags/UstFlagParserTest.cs
+++ b/OpenUtau.Test/Classic/Flags/UstFlagParserTest.cs
@@ -26,14 +26,29 @@ public void ParseTest() {
         }
 
         [Fact]
-        public void ParseSelector() {
+        public void ParsePluginSelector() {
             var result = new UstFlagParser().Parse("/1g10Mt-20");
 
-            Assert.Equal(2, result.Count);
+            Assert.Equal(3, result.Count);
+            Assert.Equal("/", result[0].Key);
+            Assert.Equal(1, result[0].Value);
+            Assert.Equal("g", result[1].Key);
+            Assert.Equal(10, result[1].Value);
+            Assert.Equal("Mt", result[2].Key);
+            Assert.Equal(-20, result[2].Value);
+        }
+
+        [Fact]
+        public void ParsePluginSelector2() {
+            var result = new UstFlagParser().Parse("g5/11t-10");
+
+            Assert.Equal(3, result.Count);
             Assert.Equal("g", result[0].Key);
-            Assert.Equal(10, result[0].Value);
-            Assert.Equal("Mt", result[1].Key);
-            Assert.Equal(-20, result[1].Value);
+            Assert.Equal(5, result[0].Value);
+            Assert.Equal("/", result[1].Key);
+            Assert.Equal(11, result[1].Value);
+            Assert.Equal("t", result[2].Key);
+            Assert.Equal(-10, result[2].Value);
         }
 
         [Fact]