diff --git a/analyzers/src/SonarAnalyzer.CSharp/Rules/RequireAttributeUsageAttribute.cs b/analyzers/src/SonarAnalyzer.CSharp/Rules/RequireAttributeUsageAttribute.cs
index 09ea59a4130..5a701a882b8 100644
--- a/analyzers/src/SonarAnalyzer.CSharp/Rules/RequireAttributeUsageAttribute.cs
+++ b/analyzers/src/SonarAnalyzer.CSharp/Rules/RequireAttributeUsageAttribute.cs
@@ -18,47 +18,41 @@
  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
-namespace SonarAnalyzer.Rules.CSharp
+namespace SonarAnalyzer.Rules.CSharp;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class RequireAttributeUsageAttribute : SonarDiagnosticAnalyzer
 {
-    [DiagnosticAnalyzer(LanguageNames.CSharp)]
-    public sealed class RequireAttributeUsageAttribute : SonarDiagnosticAnalyzer
-    {
-        internal const string DiagnosticId = "S3993";
-        private const string MessageFormat = "Specify AttributeUsage on '{0}'{1}.";
+    internal const string DiagnosticId = "S3993";
+    private const string MessageFormat = "Specify AttributeUsage on '{0}'{1}.";
 
-        private static readonly DiagnosticDescriptor rule =
-            DescriptorFactory.Create(DiagnosticId, MessageFormat);
+    private static readonly DiagnosticDescriptor Rule =
+        DescriptorFactory.Create(DiagnosticId, MessageFormat);
 
-        public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(rule);
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(Rule);
 
-        protected override void Initialize(SonarAnalysisContext context)
+    protected override void Initialize(SonarAnalysisContext context) =>
+        context.RegisterNodeAction(c =>
         {
-            context.RegisterNodeAction(c =>
-            {
-                var classDeclaration = (ClassDeclarationSyntax)c.Node;
-                var classSymbol = c.SemanticModel.GetDeclaredSymbol(classDeclaration);
-
-                if (classSymbol == null ||
-                    !classSymbol.DerivesFrom(KnownType.System_Attribute) ||
-                    classSymbol.HasAttribute(KnownType.System_AttributeUsageAttribute))
-                {
-                    return;
-                }
+            var classDeclaration = (ClassDeclarationSyntax)c.Node;
 
+            if (c.SemanticModel.GetDeclaredSymbol(classDeclaration) is { IsAbstract: false } classSymbol
+                && classSymbol.DerivesFrom(KnownType.System_Attribute)
+                && !classSymbol.HasAttribute(KnownType.System_AttributeUsageAttribute))
+            {
                 var additionalText = InheritsAttributeUsage(classSymbol)
                     ? " to improve readability, even though it inherits it from its base type"
                     : string.Empty;
 
-                c.ReportIssue(Diagnostic.Create(rule, classDeclaration.Identifier.GetLocation(),
+                c.ReportIssue(Diagnostic.Create(Rule, classDeclaration.Identifier.GetLocation(),
                     classSymbol.Name, additionalText));
-            },
-            SyntaxKind.ClassDeclaration);
-        }
-
-        private static bool InheritsAttributeUsage(INamedTypeSymbol classSymbol) =>
-            classSymbol.GetSelfAndBaseTypes()
-                // System.Attribute already has AttributeUsage, we don't want to report it
-                .TakeWhile(t => !t.Is(KnownType.System_Attribute))
-                .Any(t => t.HasAttribute(KnownType.System_AttributeUsageAttribute));
-    }
+            }
+        },
+        SyntaxKind.ClassDeclaration);
+
+    private static bool InheritsAttributeUsage(INamedTypeSymbol classSymbol) =>
+        classSymbol.GetSelfAndBaseTypes()
+            // System.Attribute already has AttributeUsage, we don't want to report it
+            .TakeWhile(x => !x.Is(KnownType.System_Attribute))
+            .Any(x => x.HasAttribute(KnownType.System_AttributeUsageAttribute));
 }
diff --git a/analyzers/tests/SonarAnalyzer.Test/Rules/MarkAssemblyWithAttributeUsageAttributeTest.cs b/analyzers/tests/SonarAnalyzer.Test/Rules/MarkAssemblyWithAttributeUsageAttributeTest.cs
index 98c99cfd699..958d1fddf28 100644
--- a/analyzers/tests/SonarAnalyzer.Test/Rules/MarkAssemblyWithAttributeUsageAttributeTest.cs
+++ b/analyzers/tests/SonarAnalyzer.Test/Rules/MarkAssemblyWithAttributeUsageAttributeTest.cs
@@ -20,13 +20,12 @@
 
 using SonarAnalyzer.Rules.CSharp;
 
-namespace SonarAnalyzer.Test.Rules
+namespace SonarAnalyzer.Test.Rules;
+
+[TestClass]
+public class MarkAssemblyWithAttributeUsageAttributeTest
 {
-    [TestClass]
-    public class MarkAssemblyWithAttributeUsageAttributeTest
-    {
-        [TestMethod]
-        public void RequireAttributeUsageAttribute() =>
-            new VerifierBuilder<RequireAttributeUsageAttribute>().AddPaths(@"RequireAttributeUsageAttribute.cs").Verify();
-    }
+    [TestMethod]
+    public void RequireAttributeUsageAttribute() =>
+        new VerifierBuilder<RequireAttributeUsageAttribute>().AddPaths(@"RequireAttributeUsageAttribute.cs").Verify();
 }
diff --git a/analyzers/tests/SonarAnalyzer.Test/Rules/RequireAttributeUsageAttributeTest.cs b/analyzers/tests/SonarAnalyzer.Test/Rules/RequireAttributeUsageAttributeTest.cs
index a8cd70f4763..bae8cb91e00 100644
--- a/analyzers/tests/SonarAnalyzer.Test/Rules/RequireAttributeUsageAttributeTest.cs
+++ b/analyzers/tests/SonarAnalyzer.Test/Rules/RequireAttributeUsageAttributeTest.cs
@@ -20,26 +20,25 @@
 
 using SonarAnalyzer.Rules.CSharp;
 
-namespace SonarAnalyzer.Test.Rules
+namespace SonarAnalyzer.Test.Rules;
+
+[TestClass]
+public class RequireAttributeUsageAttributeTest
 {
-    [TestClass]
-    public class RequireAttributeUsageAttributeTest
-    {
-        private readonly VerifierBuilder builder = new VerifierBuilder<RequireAttributeUsageAttribute>();
+    private readonly VerifierBuilder builder = new VerifierBuilder<RequireAttributeUsageAttribute>();
 
-        [TestMethod]
-        public void RequireAttributeUsageAttribute() =>
-            builder.AddPaths("RequireAttributeUsageAttribute.cs").Verify();
+    [TestMethod]
+    public void RequireAttributeUsageAttribute() =>
+        builder.AddPaths("RequireAttributeUsageAttribute.cs").Verify();
 
 #if NET
 
-        [TestMethod]
-        public void RequireAttributeUsageAttribute_CSharp11() =>
-            builder.AddPaths("RequireAttributeUsageAttribute.CSharp11.cs")
-                .WithOptions(ParseOptionsHelper.FromCSharp11)
-                .Verify();
+    [TestMethod]
+    public void RequireAttributeUsageAttribute_CSharp11() =>
+        builder.AddPaths("RequireAttributeUsageAttribute.CSharp11.cs")
+            .WithOptions(ParseOptionsHelper.FromCSharp11)
+            .Verify();
 
 #endif
 
-    }
 }
diff --git a/analyzers/tests/SonarAnalyzer.Test/TestCases/RequireAttributeUsageAttribute.cs b/analyzers/tests/SonarAnalyzer.Test/TestCases/RequireAttributeUsageAttribute.cs
index 7a31635c03e..dc3ad38dca6 100644
--- a/analyzers/tests/SonarAnalyzer.Test/TestCases/RequireAttributeUsageAttribute.cs
+++ b/analyzers/tests/SonarAnalyzer.Test/TestCases/RequireAttributeUsageAttribute.cs
@@ -1,24 +1,25 @@
 using System;
 
-namespace Tests.Diagnostics
+public class MyInvalidAttribute : Attribute
+//           ^^^^^^^^^^^^^^^^^^ {{Specify AttributeUsage on 'MyInvalidAttribute'.}}
 {
-    public class MyInvalidAttribute : Attribute
-//               ^^^^^^^^^^^^^^^^^^ {{Specify AttributeUsage on 'MyInvalidAttribute'.}}
-    {
-    }
+}
 
-    [AttributeUsage(AttributeTargets.Class)]
-    public class MyCompliantAttribute : Attribute
-    {
-    }
+[AttributeUsage(AttributeTargets.Class)]
+public class MyCompliantAttribute : Attribute
+{
+}
 
-    public class MyInvalidInheritedAttribute : MyCompliantAttribute
-//               ^^^^^^^^^^^^^^^^^^^^^^^^^^^ {{Specify AttributeUsage on 'MyInvalidInheritedAttribute' to improve readability, even though it inherits it from its base type.}}
-    {
-    }
+public class MyInvalidInheritedAttribute : MyCompliantAttribute
+//           ^^^^^^^^^^^^^^^^^^^^^^^^^^^ {{Specify AttributeUsage on 'MyInvalidInheritedAttribute' to improve readability, even though it inherits it from its base type.}}
+{
+}
 
-    [AttributeUsage(AttributeTargets.Class)]
-    public class MyInheritedAttribute : MyCompliantAttribute
-    {
-    }
+[AttributeUsage(AttributeTargets.Class)]
+public class MyInheritedAttribute : MyCompliantAttribute
+{
+}
+
+public abstract class AbstractAttribute : Attribute // Compliant
+{
 }