diff --git a/src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs b/src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs
index 824dc6f80f261..c07e760e77bbc 100644
--- a/src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs
+++ b/src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs
@@ -214,6 +214,10 @@ internal static int GetWarningLevel(ErrorCode code)
                     // Warning level 10 is exclusively for warnings introduced in the compiler
                     // shipped with dotnet 10 (C# 14) and that can be reported for pre-existing code.
                     return 10;
+                case ErrorCode.WRN_InterceptsLocationAttributeUnsupportedSignature:
+                    // Warning level 9 is exclusively for warnings introduced in the compiler
+                    // shipped with dotnet 9 (C# 13) and that can be reported for pre-existing code.
+                    return 9;
                 case ErrorCode.WRN_AddressOfInAsync:
                 case ErrorCode.WRN_ByValArraySizeConstRequired:
                     // Warning level 8 is exclusively for warnings introduced in the compiler
@@ -567,7 +571,6 @@ internal static int GetWarningLevel(ErrorCode code)
                 case ErrorCode.WRN_UninitializedNonNullableBackingField:
                 case ErrorCode.WRN_AccessorDoesNotUseBackingField:
                 case ErrorCode.WRN_UnscopedRefAttributeOldRules:
-                case ErrorCode.WRN_InterceptsLocationAttributeUnsupportedSignature:
                     return 1;
                 default:
                     return 0;
diff --git a/src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs b/src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs
index 823ea944b7d96..31372989a3f2c 100644
--- a/src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs
+++ b/src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs
@@ -14475,7 +14475,8 @@ public InterceptsLocationAttribute(string filePath, int line, int character)
                 includeCurrentAssemblyAsAnalyzerReference: false,
                 additionalFlags: ["/langversion:preview",
                     "/out:embed.exe",
-                    "/features:InterceptorsNamespaces=Generated"],
+                    "/features:InterceptorsNamespaces=Generated",
+                    "/warn:9"],
                 expectedWarningCount: 1,
                 generators: [generator],
                 analyzers: null);
@@ -14543,7 +14544,8 @@ public InterceptsLocationAttribute(string filePath, int line, int character)
                 includeCurrentAssemblyAsAnalyzerReference: false,
                 additionalFlags: ["/langversion:preview",
                     $"/out:{objDir.Path}/embed.exe",
-                    "/features:InterceptorsNamespaces=Generated"],
+                    "/features:InterceptorsNamespaces=Generated",
+                    "/warn:9"],
                 expectedWarningCount: 1,
                 generators: [generator],
                 analyzers: null);
@@ -14617,6 +14619,7 @@ public InterceptsLocationAttribute(string filePath, int line, int character)
                     "/langversion:preview",
                     "/out:embed.exe",
                     "/features:InterceptorsNamespaces=Generated",
+                    "/warn:9",
                     .. string.IsNullOrEmpty(pathMapArgument) ? default(Span<string>) : [pathMapArgument]
                     ],
                 expectedWarningCount: 1,
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/InterceptorsTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/InterceptorsTests.cs
index 5789d0bf7059d..960e0e7476c0c 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/InterceptorsTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/InterceptorsTests.cs
@@ -49,6 +49,43 @@ public InterceptsLocationAttribute(int version, string data) { }
 
     private static string GetAttributeArgs(InterceptableLocation location) => $@"{location.Version}, ""{location.Data}""";
 
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/76641")]
+    public void UnsupportedWarningWave()
+    {
+        var source = ("""
+            C.M();
+
+            class C
+            {
+                public static void M() => throw null!;
+            }
+            """, "Program.cs");
+        var interceptors = $$"""
+            using System.Runtime.CompilerServices;
+            using System;
+            class D
+            {
+                [InterceptsLocation("Program.cs", 1, 3)]
+                public static void M() => Console.Write(1);
+            }
+            """;
+
+        var comp = CreateCompilation([source, interceptors, s_attributesSource], parseOptions: RegularWithInterceptors, options: TestOptions.DebugExe.WithWarningLevel(8));
+        comp.VerifyEmitDiagnostics();
+
+        comp = CreateCompilation([source, interceptors, s_attributesSource], parseOptions: RegularWithInterceptors, options: TestOptions.DebugExe.WithWarningLevel(9));
+        comp.VerifyEmitDiagnostics(
+            // (5,6): warning CS9270: 'InterceptsLocationAttribute(string, int, int)' is not supported. Move to 'InterceptableLocation'-based generation of these attributes instead. (https://github.com/dotnet/roslyn/issues/72133)
+            //     [InterceptsLocation("Program.cs", 1, 3)]
+            Diagnostic(ErrorCode.WRN_InterceptsLocationAttributeUnsupportedSignature, @"InterceptsLocation(""Program.cs"", 1, 3)").WithLocation(5, 6));
+
+        comp = CreateCompilation([source, interceptors, s_attributesSource], parseOptions: RegularWithInterceptors);
+        comp.VerifyEmitDiagnostics(
+            // (5,6): warning CS9270: 'InterceptsLocationAttribute(string, int, int)' is not supported. Move to 'InterceptableLocation'-based generation of these attributes instead. (https://github.com/dotnet/roslyn/issues/72133)
+            //     [InterceptsLocation("Program.cs", 1, 3)]
+            Diagnostic(ErrorCode.WRN_InterceptsLocationAttributeUnsupportedSignature, @"InterceptsLocation(""Program.cs"", 1, 3)").WithLocation(5, 6));
+    }
+
     [Fact]
     public void FeatureFlag()
     {
diff --git a/src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs b/src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs
index e7b00a93471b3..e2c7ddb41920c 100644
--- a/src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs
+++ b/src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs
@@ -437,7 +437,6 @@ public void WarningLevel_2()
                         case ErrorCode.WRN_FieldIsAmbiguous:
                         case ErrorCode.WRN_UninitializedNonNullableBackingField:
                         case ErrorCode.WRN_AccessorDoesNotUseBackingField:
-                        case ErrorCode.WRN_InterceptsLocationAttributeUnsupportedSignature:
                             Assert.Equal(1, ErrorFacts.GetWarningLevel(errorCode));
                             break;
                         case ErrorCode.WRN_InvalidVersionFormat:
@@ -475,6 +474,10 @@ public void WarningLevel_2()
                             // These are the warnings introduced with the warning "wave" shipped with dotnet 8 and C# 12.
                             Assert.Equal(8, ErrorFacts.GetWarningLevel(errorCode));
                             break;
+                        case ErrorCode.WRN_InterceptsLocationAttributeUnsupportedSignature:
+                            // These are the warnings introduced with the warning "wave" shipped with dotnet 9 and C# 13.
+                            Assert.Equal(9, ErrorFacts.GetWarningLevel(errorCode));
+                            break;
                         case ErrorCode.WRN_UnassignedInternalRefField:
                             // These are the warnings introduced with the warning "wave" shipped with dotnet 10 and C# 14.
                             Assert.Equal(10, ErrorFacts.GetWarningLevel(errorCode));