diff --git a/ChangeLog.md b/ChangeLog.md
index a76362b8e0..4066e8867d 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fix [RCS1234](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1234) ([PR](https://github.com/dotnet/roslynator/pull/1233))
+
 ## [4.6.1] - 2023-10-23
 
 ### Fixed
diff --git a/src/Analyzers.CodeFixes/CSharp/CodeFixes/EnumMemberDeclarationCodeFixProvider.cs b/src/Analyzers.CodeFixes/CSharp/CodeFixes/EnumMemberDeclarationCodeFixProvider.cs
index 1c282cec2e..c6795c2f89 100644
--- a/src/Analyzers.CodeFixes/CSharp/CodeFixes/EnumMemberDeclarationCodeFixProvider.cs
+++ b/src/Analyzers.CodeFixes/CSharp/CodeFixes/EnumMemberDeclarationCodeFixProvider.cs
@@ -194,6 +194,9 @@ private static EnumMemberDeclarationSyntax FindMemberByValue(
         {
             IFieldSymbol fieldSymbol = semanticModel.GetDeclaredSymbol(enumMember, cancellationToken);
 
+            if (CSharpUtility.IsSymbolObsolete(fieldSymbol))
+                continue;
+
             if (!SymbolEqualityComparer.Default.Equals(fieldSymbolInfo.Symbol, fieldSymbol))
             {
                 EnumFieldSymbolInfo fieldSymbolInfo2 = EnumFieldSymbolInfo.Create(fieldSymbol);
diff --git a/src/Analyzers/CSharp/Analysis/EnumSymbolAnalyzer.cs b/src/Analyzers/CSharp/Analysis/EnumSymbolAnalyzer.cs
index 27850aed95..5bad422e50 100644
--- a/src/Analyzers/CSharp/Analysis/EnumSymbolAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analysis/EnumSymbolAnalyzer.cs
@@ -196,6 +196,10 @@ private static void AnalyzeNamedType(SymbolAnalysisContext context)
                         continue;
                     }
 
+                    if (CSharpUtility.IsSymbolObsolete(symbolInfo1.Symbol)
+                        || CSharpUtility.IsSymbolObsolete(symbolInfo2.Symbol))
+                        continue;
+
                     var enumMember1 = (EnumMemberDeclarationSyntax)symbolInfo1.Symbol.GetSyntax(context.CancellationToken);
 
                     if (enumMember1 is null)
diff --git a/src/CSharp/CSharp/CSharpUtility.cs b/src/CSharp/CSharp/CSharpUtility.cs
index d0e5e36ba6..62cdac0af9 100644
--- a/src/CSharp/CSharp/CSharpUtility.cs
+++ b/src/CSharp/CSharp/CSharpUtility.cs
@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation and Contributors. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
 using System.Threading;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
@@ -681,4 +680,9 @@ public static SeparatedSyntaxList<TypeParameterSyntax> GetTypeParameters(SyntaxN
                 return null;
         }
     }
+
+    public static bool IsSymbolObsolete(ISymbol symbol)
+    {
+        return symbol.HasAttribute(MetadataNames.System_ObsoleteAttribute);
+    }
 }
diff --git a/src/Tests/Analyzers.Tests/RCS1234DuplicateEnumValueTests.cs b/src/Tests/Analyzers.Tests/RCS1234DuplicateEnumValueTests.cs
index 19322b887e..c15143a404 100644
--- a/src/Tests/Analyzers.Tests/RCS1234DuplicateEnumValueTests.cs
+++ b/src/Tests/Analyzers.Tests/RCS1234DuplicateEnumValueTests.cs
@@ -114,6 +114,34 @@ enum E
 ");
     }
 
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.DuplicateEnumValue)]
+    public async Task Test6()
+    {
+        await VerifyDiagnosticAndFixAsync(@"
+using System;
+
+enum E
+{
+    [Obsolete]
+    A = 1,
+
+    B = 1,
+    C = [|1|]
+}
+", @"
+using System;
+
+enum E
+{
+    [Obsolete]
+    A = 1,
+
+    B = 1,
+    C = B
+}
+");
+    }
+
     [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.DuplicateEnumValue)]
     public async Task TestNoDiagnostic()
     {
@@ -124,4 +152,20 @@ enum E
     B = A
 }");
     }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.DuplicateEnumValue)]
+    public async Task TestNoDiagnostic2()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System;
+
+enum E
+{
+    [Obsolete]
+    A = 1,
+
+    B = 1,
+}
+");
+    }
 }