diff --git a/src/Analyzers/CSharp/Tests/RemoveUnnecessarySuppressions/RemoveUnnecessaryAttributeSuppressionsTests.cs b/src/Analyzers/CSharp/Tests/RemoveUnnecessarySuppressions/RemoveUnnecessaryAttributeSuppressionsTests.cs
index 03c6ac49623ca..8e68f85e67c30 100644
--- a/src/Analyzers/CSharp/Tests/RemoveUnnecessarySuppressions/RemoveUnnecessaryAttributeSuppressionsTests.cs
+++ b/src/Analyzers/CSharp/Tests/RemoveUnnecessarySuppressions/RemoveUnnecessaryAttributeSuppressionsTests.cs
@@ -5,6 +5,7 @@
 #nullable enable
 
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.RemoveUnnecessarySuppressions;
 using Microsoft.CodeAnalysis.Test.Utilities;
 using Roslyn.Test.Utilities;
 using Xunit;
@@ -182,5 +183,23 @@ public void M() {{ }}
 }}";
             await VerifyCS.VerifyCodeFixAsync(input, input);
         }
+
+        [Fact, WorkItem(45465, "https://github.com/dotnet/roslyn/issues/45465")]
+        public async Task LegacyModeGlobalSuppressionWithNamespaceAndDescendantsScope()
+        {
+            var target = "N:N.InvalidChild";
+            var input = $@"
+[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage(""Category"", ""Id: Title"", Scope = ""namespaceanddescendants"", Target = {{|#0:""{target}""|}})]
+
+namespace N
+{{
+    class C {{ }}
+}}";
+            var expectedDiagnostic = VerifyCS.Diagnostic(AbstractRemoveUnnecessaryAttributeSuppressionsDiagnosticAnalyzer.LegacyFormatTargetDescriptor)
+                                        .WithLocation(0)
+                                        .WithArguments(target);
+
+            await VerifyCS.VerifyCodeFixAsync(input, expectedDiagnostic, input);
+        }
     }
 }
diff --git a/src/Analyzers/Core/Analyzers/RemoveUnnecessarySuppressions/SuppressMessageAttributeState.cs b/src/Analyzers/Core/Analyzers/RemoveUnnecessarySuppressions/SuppressMessageAttributeState.cs
index f4e7b3990db5f..d1e8d9be2ea77 100644
--- a/src/Analyzers/Core/Analyzers/RemoveUnnecessarySuppressions/SuppressMessageAttributeState.cs
+++ b/src/Analyzers/Core/Analyzers/RemoveUnnecessarySuppressions/SuppressMessageAttributeState.cs
@@ -127,6 +127,11 @@ public bool HasValidTarget(
                 // Compilation wide suppression with a non-null target is considered invalid.
                 return targetSymbolString == null;
             }
+            else if (targetScope == TargetScope.NamespaceAndDescendants)
+            {
+                // TargetSymbolResolver expects the callers to normalize 'NamespaceAndDescendants' and 'Namespace' scopes to 'Namespace' scope.
+                targetScope = TargetScope.Namespace;
+            }
 
             var resolver = new TargetSymbolResolver(_compilation, targetScope, targetSymbolString);
             resolvedSymbols = resolver.Resolve(out targetHasDocCommentIdFormat);