diff --git a/src/EditorFeatures/CSharpTest/Diagnostics/Nullable/CSharpDeclareAsNullableCodeFixTests.cs b/src/EditorFeatures/CSharpTest/Diagnostics/Nullable/CSharpDeclareAsNullableCodeFixTests.cs
index 9a49294320dd5..66b792e6f20f3 100644
--- a/src/EditorFeatures/CSharpTest/Diagnostics/Nullable/CSharpDeclareAsNullableCodeFixTests.cs
+++ b/src/EditorFeatures/CSharpTest/Diagnostics/Nullable/CSharpDeclareAsNullableCodeFixTests.cs
@@ -832,6 +832,22 @@ void M2(string? x) { }
 }", parameters: s_nullableFeature);
         }
 
+        [Fact]
+        [WorkItem(44338, "https://github.com/dotnet/roslyn/issues/44338")]
+        public async Task NoFixInvocationOfExternalMethod_NamedArgument()
+        {
+            await TestMissingInRegularAndScriptAsync(
+@"#nullable enable
+class Program
+{
+    void M()
+    {
+        var list = new System.Collections.Generic.List<string>();
+        list.Add(item: [|null|]);
+    }
+}", parameters: s_nullableFeature);
+        }
+
         [Fact]
         public async Task FixInvocation_NamedArgument_OutOfOrder()
         {
@@ -856,6 +872,22 @@ void M2(int i, string? x) { }
 }", parameters: s_nullableFeature);
         }
 
+        [Fact]
+        [WorkItem(44338, "https://github.com/dotnet/roslyn/issues/44338")]
+        public async Task NoFixInvocationOfExternalMethod_NamedArgument_OutOfOrder()
+        {
+            await TestMissingInRegularAndScriptAsync(
+@"#nullable enable
+class Program
+{
+    void M()
+    {
+        var dict = new System.Collections.Generic.Dictionary<string, int>();
+        dict.Add(value: 0, key: [|null|]);
+    }
+}", parameters: s_nullableFeature);
+        }
+
         [Fact]
         public async Task FixInvocation_NamedArgument_Partial()
         {
@@ -896,6 +928,22 @@ void M2(string? x) { }
 }", parameters: s_nullableFeature);
         }
 
+        [Fact]
+        [WorkItem(44338, "https://github.com/dotnet/roslyn/issues/44338")]
+        public async Task NoFixInvocationOfExternalMethod_PositionArgument()
+        {
+            await TestMissingInRegularAndScriptAsync(
+@"#nullable enable
+class Program
+{
+    void M()
+    {
+        var list = new System.Collections.Generic.List<string>();
+        list.Add([|null|]);
+    }
+}", parameters: s_nullableFeature);
+        }
+
         [Fact]
         public async Task FixInvocation_PositionArgument_SecondPosition()
         {
diff --git a/src/Features/CSharp/Portable/CodeFixes/Nullable/CSharpDeclareAsNullableCodeFixProvider.cs b/src/Features/CSharp/Portable/CodeFixes/Nullable/CSharpDeclareAsNullableCodeFixProvider.cs
index 9bde063178b72..5272750ef3986 100644
--- a/src/Features/CSharp/Portable/CodeFixes/Nullable/CSharpDeclareAsNullableCodeFixProvider.cs
+++ b/src/Features/CSharp/Portable/CodeFixes/Nullable/CSharpDeclareAsNullableCodeFixProvider.cs
@@ -340,7 +340,7 @@ declarator.Parent is VariableDeclarationSyntax declaration &&
             static TypeSyntax? TryGetParameterTypeSyntax(IParameterSymbol? parameterSymbol)
             {
                 if (parameterSymbol is object &&
-                    parameterSymbol.DeclaringSyntaxReferences[0].GetSyntax() is ParameterSyntax parameterSyntax &&
+                    parameterSymbol.DeclaringSyntaxReferences.FirstOrDefault()?.GetSyntax() is ParameterSyntax parameterSyntax &&
                     parameterSymbol.ContainingSymbol is IMethodSymbol method &&
                     method.GetAllMethodSymbolsOfPartialParts().Length == 1)
                 {