diff --git a/grammars/csharp.tmLanguage b/grammars/csharp.tmLanguage
index 4064c73..4f47c06 100644
--- a/grammars/csharp.tmLanguage
+++ b/grammars/csharp.tmLanguage
@@ -6872,11 +6872,32 @@
             <key>name</key>
             <string>storage.modifier.cs</string>
             <key>match</key>
-            <string>\b(ref|out|in)\b</string>
+            <string>\b(ref|in)\b</string>
           </dict>
           <dict>
-            <key>include</key>
-            <string>#declaration-expression-local</string>
+            <key>begin</key>
+            <string>\b(out)\b</string>
+            <key>beginCaptures</key>
+            <dict>
+              <key>1</key>
+              <dict>
+                <key>name</key>
+                <string>storage.modifier.cs</string>
+              </dict>
+            </dict>
+            <key>end</key>
+            <string>(?=,|\)|\])</string>
+            <key>patterns</key>
+            <array>
+              <dict>
+                <key>include</key>
+                <string>#declaration-expression-local</string>
+              </dict>
+              <dict>
+                <key>include</key>
+                <string>#expression</string>
+              </dict>
+            </array>
           </dict>
           <dict>
             <key>include</key>
diff --git a/grammars/csharp.tmLanguage.cson b/grammars/csharp.tmLanguage.cson
index 17c3db2..e5acf75 100644
--- a/grammars/csharp.tmLanguage.cson
+++ b/grammars/csharp.tmLanguage.cson
@@ -4141,10 +4141,22 @@ repository:
     patterns: [
       {
         name: "storage.modifier.cs"
-        match: "\\b(ref|out|in)\\b"
+        match: "\\b(ref|in)\\b"
       }
       {
-        include: "#declaration-expression-local"
+        begin: "\\b(out)\\b"
+        beginCaptures:
+          "1":
+            name: "storage.modifier.cs"
+        end: "(?=,|\\)|\\])"
+        patterns: [
+          {
+            include: "#declaration-expression-local"
+          }
+          {
+            include: "#expression"
+          }
+        ]
       }
       {
         include: "#expression"
diff --git a/src/csharp.tmLanguage.yml b/src/csharp.tmLanguage.yml
index 4648f6b..35f45fb 100644
--- a/src/csharp.tmLanguage.yml
+++ b/src/csharp.tmLanguage.yml
@@ -2753,8 +2753,14 @@ repository:
   argument:
     patterns:
     - name: storage.modifier.cs
-      match: \b(ref|out|in)\b
-    - include: '#declaration-expression-local'
+      match: \b(ref|in)\b
+    - begin: \b(out)\b
+      beginCaptures:
+        '1': { name: storage.modifier.cs }
+      end: (?=,|\)|\])
+      patterns:
+      - include: '#declaration-expression-local'
+      - include: '#expression'
     - include: '#expression'
 
   query-expression:
diff --git a/test/expressions.tests.ts b/test/expressions.tests.ts
index 5b713bb..902f494 100644
--- a/test/expressions.tests.ts
+++ b/test/expressions.tests.ts
@@ -2112,28 +2112,6 @@ var result = list.Select(l => new {
         ]);
       });
 
-      it("in argument declaration", async () => {
-        const input = Input.InMethod(`var o = P[in int x, in var y];`);
-        const tokens = await tokenize(input);
-
-        tokens.should.deep.equal([
-          Token.Keywords.Var,
-          Token.Identifiers.LocalName("o"),
-          Token.Operators.Assignment,
-          Token.Variables.Property("P"),
-          Token.Punctuation.OpenBracket,
-          Token.Keywords.Modifiers.In,
-          Token.PrimitiveType.Int,
-          Token.Identifiers.LocalName("x"),
-          Token.Punctuation.Comma,
-          Token.Keywords.Modifiers.In,
-          Token.Keywords.Var,
-          Token.Identifiers.LocalName("y"),
-          Token.Punctuation.CloseBracket,
-          Token.Punctuation.Semicolon
-        ]);
-      });
-
       it("member of generic with no arguments", async () => {
         const input = Input.InMethod(`var o = C<int>.P[];`);
         const tokens = await tokenize(input);
@@ -2644,25 +2622,6 @@ long total = (data["bonusGame"]["win"].AsLong) * data["bonusGame"]["betMult"].As
         ]);
       });
 
-      it("in argument declaration", async () => {
-        const input = Input.InMethod(`M(in int x, in var y);`);
-        const tokens = await tokenize(input);
-
-        tokens.should.deep.equal([
-          Token.Identifiers.MethodName("M"),
-          Token.Punctuation.OpenParen,
-          Token.Keywords.Modifiers.In,
-          Token.PrimitiveType.Int,
-          Token.Identifiers.LocalName("x"),
-          Token.Punctuation.Comma,
-          Token.Keywords.Modifiers.In,
-          Token.Keywords.Var,
-          Token.Identifiers.LocalName("y"),
-          Token.Punctuation.CloseParen,
-          Token.Punctuation.Semicolon
-        ]);
-      });
-
       it("generic with no arguments", async () => {
         const input = Input.InMethod(`M<int>();`);
         const tokens = await tokenize(input);