diff --git a/src/Mvc/Mvc.Core/src/ApiExplorer/IApiRequestFormatMetadataProvider.cs b/src/Mvc/Mvc.Core/src/ApiExplorer/IApiRequestFormatMetadataProvider.cs
index cfb942053215..50e84006030d 100644
--- a/src/Mvc/Mvc.Core/src/ApiExplorer/IApiRequestFormatMetadataProvider.cs
+++ b/src/Mvc/Mvc.Core/src/ApiExplorer/IApiRequestFormatMetadataProvider.cs
@@ -25,6 +25,6 @@ public interface IApiRequestFormatMetadataProvider
     /// </param>
     /// <returns>Content types which are supported by the <see cref="Formatters.IInputFormatter"/>.</returns>
     IReadOnlyList<string>? GetSupportedContentTypes(
-        string contentType,
+        string? contentType,
         Type objectType);
 }
diff --git a/src/Mvc/Mvc.Core/src/Formatters/InputFormatter.cs b/src/Mvc/Mvc.Core/src/Formatters/InputFormatter.cs
index 2474e63ab177..47a6fa1b5b27 100644
--- a/src/Mvc/Mvc.Core/src/Formatters/InputFormatter.cs
+++ b/src/Mvc/Mvc.Core/src/Formatters/InputFormatter.cs
@@ -118,7 +118,7 @@ public virtual Task<InputFormatterResult> ReadAsync(InputFormatterContext contex
     public abstract Task<InputFormatterResult> ReadRequestBodyAsync(InputFormatterContext context);
 
     /// <inheritdoc />
-    public virtual IReadOnlyList<string>? GetSupportedContentTypes(string contentType, Type objectType)
+    public virtual IReadOnlyList<string>? GetSupportedContentTypes(string? contentType, Type objectType)
     {
         if (SupportedMediaTypes.Count == 0)
         {
diff --git a/src/Mvc/Mvc.Core/src/PublicAPI.Shipped.txt b/src/Mvc/Mvc.Core/src/PublicAPI.Shipped.txt
index ebb18238569f..824fa9ceec9d 100644
--- a/src/Mvc/Mvc.Core/src/PublicAPI.Shipped.txt
+++ b/src/Mvc/Mvc.Core/src/PublicAPI.Shipped.txt
@@ -172,7 +172,7 @@ Microsoft.AspNetCore.Mvc.ApiExplorer.IApiDescriptionGroupNameProvider.GroupName.
 Microsoft.AspNetCore.Mvc.ApiExplorer.IApiDescriptionVisibilityProvider
 Microsoft.AspNetCore.Mvc.ApiExplorer.IApiDescriptionVisibilityProvider.IgnoreApi.get -> bool
 Microsoft.AspNetCore.Mvc.ApiExplorer.IApiRequestFormatMetadataProvider
-Microsoft.AspNetCore.Mvc.ApiExplorer.IApiRequestFormatMetadataProvider.GetSupportedContentTypes(string! contentType, System.Type! objectType) -> System.Collections.Generic.IReadOnlyList<string!>?
+Microsoft.AspNetCore.Mvc.ApiExplorer.IApiRequestFormatMetadataProvider.GetSupportedContentTypes(string? contentType, System.Type! objectType) -> System.Collections.Generic.IReadOnlyList<string!>?
 Microsoft.AspNetCore.Mvc.ApiExplorer.IApiRequestMetadataProvider
 Microsoft.AspNetCore.Mvc.ApiExplorer.IApiRequestMetadataProvider.SetContentTypes(Microsoft.AspNetCore.Mvc.Formatters.MediaTypeCollection! contentTypes) -> void
 Microsoft.AspNetCore.Mvc.ApiExplorer.IApiResponseMetadataProvider
@@ -2454,7 +2454,7 @@ virtual Microsoft.AspNetCore.Mvc.Formatters.FormatFilter.GetFormat(Microsoft.Asp
 virtual Microsoft.AspNetCore.Mvc.Formatters.InputFormatter.CanRead(Microsoft.AspNetCore.Mvc.Formatters.InputFormatterContext! context) -> bool
 virtual Microsoft.AspNetCore.Mvc.Formatters.InputFormatter.CanReadType(System.Type! type) -> bool
 virtual Microsoft.AspNetCore.Mvc.Formatters.InputFormatter.GetDefaultValueForType(System.Type! modelType) -> object?
-virtual Microsoft.AspNetCore.Mvc.Formatters.InputFormatter.GetSupportedContentTypes(string! contentType, System.Type! objectType) -> System.Collections.Generic.IReadOnlyList<string!>?
+virtual Microsoft.AspNetCore.Mvc.Formatters.InputFormatter.GetSupportedContentTypes(string? contentType, System.Type! objectType) -> System.Collections.Generic.IReadOnlyList<string!>?
 virtual Microsoft.AspNetCore.Mvc.Formatters.InputFormatter.ReadAsync(Microsoft.AspNetCore.Mvc.Formatters.InputFormatterContext! context) -> System.Threading.Tasks.Task<Microsoft.AspNetCore.Mvc.Formatters.InputFormatterResult!>!
 virtual Microsoft.AspNetCore.Mvc.Formatters.OutputFormatter.CanWriteResult(Microsoft.AspNetCore.Mvc.Formatters.OutputFormatterCanWriteContext! context) -> bool
 virtual Microsoft.AspNetCore.Mvc.Formatters.OutputFormatter.CanWriteType(System.Type? type) -> bool