diff --git a/ChangeLog.md b/ChangeLog.md
index 2d66503da0..1d60fb0fe7 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -36,6 +36,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix [RCS1208](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1208.md) ([#1119](https://github.com/JosefPihrt/Roslynator/pull/1119)).
 - [CLI] Fix member full declaration in generated documentation (command `generate-doc`) ([#1130](https://github.com/josefpihrt/roslynator/pull/1130)).
   - Append `?` to nullable reference types.
+- Fix [RCS1179](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1179.md) ([#1129](https://github.com/JosefPihrt/Roslynator/pull/1129)).
 
 ## [4.3.0] - 2023-04-24
 
diff --git a/src/Analyzers/CSharp/Analysis/UnnecessaryAssignmentAnalyzer.cs b/src/Analyzers/CSharp/Analysis/UnnecessaryAssignmentAnalyzer.cs
index d992e996a6..308ef81bcd 100644
--- a/src/Analyzers/CSharp/Analysis/UnnecessaryAssignmentAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analysis/UnnecessaryAssignmentAnalyzer.cs
@@ -70,6 +70,8 @@ private static void AnalyzeIfStatement(SyntaxNodeAnalysisContext context)
         if (!IsLocalDeclaredInScopeOrNonRefOrOutParameterOfEnclosingSymbol(symbol, statementsInfo.Parent, semanticModel, cancellationToken))
             return;
 
+        ITypeSymbol returnTypeSymbol = semanticModel.GetTypeSymbol(expression, cancellationToken);
+
         foreach (IfStatementOrElseClause ifOrElse in ifStatement.AsCascade())
         {
             StatementSyntax statement = ifOrElse.Statement;
@@ -78,7 +80,7 @@ private static void AnalyzeIfStatement(SyntaxNodeAnalysisContext context)
                 statement = ((BlockSyntax)statement).Statements.LastOrDefault();
 
             if (!statement.IsKind(SyntaxKind.ThrowStatement)
-                && !IsSymbolAssignedInStatement(symbol, statement, semanticModel, cancellationToken))
+                && !IsSymbolAssignedInStatementWithCorrectType(symbol, statement, semanticModel, returnTypeSymbol, cancellationToken))
             {
                 return;
             }
@@ -113,6 +115,7 @@ private static void AnalyzeSwitchStatement(SyntaxNodeAnalysisContext context)
         CancellationToken cancellationToken = context.CancellationToken;
 
         ISymbol symbol = semanticModel.GetSymbol(expression, cancellationToken);
+        ITypeSymbol returnTypeSymbol = semanticModel.GetTypeInfo(expression, cancellationToken).Type;
 
         if (symbol is null)
             return;
@@ -136,7 +139,7 @@ private static void AnalyzeSwitchStatement(SyntaxNodeAnalysisContext context)
                 case SyntaxKind.BreakStatement:
                     {
                         if (statements.Count == 1
-                            || !IsSymbolAssignedInStatement(symbol, statements.LastButOne(), semanticModel, cancellationToken))
+                            || !IsSymbolAssignedInStatementWithCorrectType(symbol, statements.LastButOne(), semanticModel, returnTypeSymbol, cancellationToken))
                         {
                             return;
                         }
@@ -204,11 +207,12 @@ private static bool IsLocalDeclaredInScopeOrNonRefOrOutParameterOfEnclosingSymbo
         return false;
     }
 
-    private static bool IsSymbolAssignedInStatement(ISymbol symbol, StatementSyntax statement, SemanticModel semanticModel, CancellationToken cancellationToken)
+    private static bool IsSymbolAssignedInStatementWithCorrectType(ISymbol symbol, StatementSyntax statement, SemanticModel semanticModel, ITypeSymbol typeSymbol, CancellationToken cancellationToken)
     {
         SimpleAssignmentStatementInfo assignmentInfo = SyntaxInfo.SimpleAssignmentStatementInfo(statement);
 
         return assignmentInfo.Success
-            && SymbolEqualityComparer.Default.Equals(semanticModel.GetSymbol(assignmentInfo.Left, cancellationToken), symbol);
+            && SymbolEqualityComparer.Default.Equals(semanticModel.GetSymbol(assignmentInfo.Left, cancellationToken), symbol)
+            && SymbolEqualityComparer.Default.Equals(typeSymbol, semanticModel.GetTypeSymbol(assignmentInfo.Right, cancellationToken));
     }
 }
diff --git a/src/Tests/Analyzers.Tests/RCS1179UnnecessaryAssignmentTests.cs b/src/Tests/Analyzers.Tests/RCS1179UnnecessaryAssignmentTests.cs
index 49b8ffdb9b..f81cdd15b7 100644
--- a/src/Tests/Analyzers.Tests/RCS1179UnnecessaryAssignmentTests.cs
+++ b/src/Tests/Analyzers.Tests/RCS1179UnnecessaryAssignmentTests.cs
@@ -309,6 +309,67 @@ int M()
         }
     }
 }
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UnnecessaryAssignment)]
+    public async Task Test_NoDiagnostic_ForPolymorphicIf()
+    {
+        await VerifyNoDiagnosticAsync(
+            @"
+class A {}
+class B {}
+class C
+{
+    void M()
+    {
+        var fun = (bool flag) =>
+        {
+            object x;
+            if (flag)
+            {
+                x = new A();
+            }
+            else
+            {
+                x = new B();
+            }
+
+            return x;
+        };
+    }
+}
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UnnecessaryAssignment)]
+    public async Task Test_NoDiagnostic_ForPolymorphicSwitch()
+    {
+        await VerifyNoDiagnosticAsync(
+            @"
+class A {}
+class B {}
+class C
+{
+    void M()
+    {
+        var fun = (object o) =>
+        {
+            object x;
+            switch(o)
+            {
+                case int:
+                    x = new A();
+                    break;
+                default:
+                    x = new B();
+                    break;
+            }
+
+            return x;
+        };
+    }
+}
 ");
     }
 }