diff --git a/CHANGELIST.md b/CHANGELIST.md
index b4e6668c..c6c7bcd8 100644
--- a/CHANGELIST.md
+++ b/CHANGELIST.md
@@ -7,6 +7,7 @@
 - Add generic drive flag for Redumper
 - Handle numeric disc titles as issue numbers
 - Unify handling of enable/disable events
+- Enable nullability in Check
 
 ### 2.7.0 (2023-10-11)
 
diff --git a/MPF.Check/MPF.Check.csproj b/MPF.Check/MPF.Check.csproj
index d78c09a9..e4016cda 100644
--- a/MPF.Check/MPF.Check.csproj
+++ b/MPF.Check/MPF.Check.csproj
@@ -11,6 +11,10 @@
     <VersionPrefix>2.7.0</VersionPrefix>
   </PropertyGroup>
 
+  <PropertyGroup Condition="'$(TargetFramework)'!='net48'">
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
   <ItemGroup>
     <None Include="App.config" />
   </ItemGroup>
diff --git a/MPF.Check/Program.cs b/MPF.Check/Program.cs
index 9116cdc5..ee75f033 100644
--- a/MPF.Check/Program.cs
+++ b/MPF.Check/Program.cs
@@ -21,7 +21,7 @@ namespace MPF.Check
             }
 
             // Try processing the common arguments
-            (bool success, MediaType mediaType, RedumpSystem? knownSystem, string error) = OptionsLoader.ProcessCommonArguments(args);
+            (bool success, MediaType mediaType, RedumpSystem? knownSystem, var error) = OptionsLoader.ProcessCommonArguments(args);
             if (!success)
             {
                 DisplayHelp(error);
@@ -29,11 +29,7 @@ namespace MPF.Check
             }
 
             // Loop through and process options
-#if NET48
-            (Core.Data.Options options, SubmissionInfo seedInfo, string path, int startIndex) = OptionsLoader.LoadFromArguments(args, startIndex: 2);
-#else
-            (Core.Data.Options options, SubmissionInfo? seedInfo, string? path, int startIndex) = OptionsLoader.LoadFromArguments(args, startIndex: 2);
-#endif
+            (var options, var seedInfo, var path, int startIndex) = OptionsLoader.LoadFromArguments(args, startIndex: 2);
             if (options.InternalProgram == InternalProgram.NONE)
             {
                 DisplayHelp("A program name needs to be provided");
@@ -50,7 +46,7 @@ namespace MPF.Check
 #if NET48
             (bool? _, string message) = RedumpWebClient.ValidateCredentials(options?.RedumpUsername, options?.RedumpPassword);
 #else
-            (bool? _, string message) = RedumpHttpClient.ValidateCredentials(options?.RedumpUsername, options?.RedumpPassword).ConfigureAwait(false).GetAwaiter().GetResult();
+            (bool? _, string? message) = RedumpHttpClient.ValidateCredentials(options.RedumpUsername ?? string.Empty, options.RedumpPassword ?? string.Empty).ConfigureAwait(false).GetAwaiter().GetResult();
 #endif
             if (!string.IsNullOrWhiteSpace(message))
                 Console.WriteLine(message);
@@ -69,7 +65,11 @@ namespace MPF.Check
                 string filepath = Path.GetFullPath(args[i].Trim('"'));
 
                 // Now populate an environment
+#if NET48
                 Drive drive = null;
+#else
+                Drive? drive = null;
+#endif
                 if (!string.IsNullOrWhiteSpace(path))
                     drive = Drive.Create(null, path);
 
@@ -85,7 +85,11 @@ namespace MPF.Check
         /// Display help for MPF.Check
         /// </summary>
         /// <param name="error">Error string to prefix the help text with</param>
+#if NET48
         private static void DisplayHelp(string error = null)
+#else
+        private static void DisplayHelp(string? error = null)
+#endif
         {
             if (error != null)
                 Console.WriteLine(error);
diff --git a/MPF.Core/ConsoleLogger.cs b/MPF.Core/ConsoleLogger.cs
index c7082961..107c214e 100644
--- a/MPF.Core/ConsoleLogger.cs
+++ b/MPF.Core/ConsoleLogger.cs
@@ -9,7 +9,11 @@ namespace MPF.Core
         /// <summary>
         /// Simple process counter to write to console
         /// </summary>
+#if NET48
         public static void ProgressUpdated(object sender, Result value)
+#else
+        public static void ProgressUpdated(object? sender, Result value)
+#endif
         {
             Console.WriteLine(value.Message);
         }
@@ -17,7 +21,11 @@ namespace MPF.Core
         /// <summary>
         /// Simple process counter to write to console
         /// </summary>
+#if NET48
         public static void ProgressUpdated(object sender, ProtectionProgress value)
+#else
+        public static void ProgressUpdated(object? sender, ProtectionProgress value)
+#endif
         {
             Console.WriteLine($"{value.Percentage * 100:N2}%: {value.Filename} - {value.Protection}");
         }
diff --git a/MPF.Core/DumpEnvironment.cs b/MPF.Core/DumpEnvironment.cs
index cb9b925e..c8274410 100644
--- a/MPF.Core/DumpEnvironment.cs
+++ b/MPF.Core/DumpEnvironment.cs
@@ -123,7 +123,11 @@ namespace MPF.Core
             RedumpSystem? system,
             MediaType? type,
             InternalProgram? internalProgram,
+#if NET48
             string parameters)
+#else
+            string? parameters)
+#endif
         {
             // Set options object
             this.Options = options;
@@ -194,7 +198,11 @@ namespace MPF.Core
         /// Set the parameters object based on the internal program and parameters string
         /// </summary>
         /// <param name="parameters">String representation of the parameters</param>
+#if NET48
         public void SetParameters(string parameters)
+#else
+        public void SetParameters(string? parameters)
+#endif
         {
             switch (this.InternalProgram)
             {
@@ -284,7 +292,7 @@ namespace MPF.Core
             return null;
         }
 
-        #endregion
+#endregion
 
         #region Dumping
 
diff --git a/MPF.Core/Modules/Aaru/Parameters.cs b/MPF.Core/Modules/Aaru/Parameters.cs
index aa6f1b07..41e455ce 100644
--- a/MPF.Core/Modules/Aaru/Parameters.cs
+++ b/MPF.Core/Modules/Aaru/Parameters.cs
@@ -256,7 +256,11 @@ namespace MPF.Core.Modules.Aaru
         #endregion
 
         /// <inheritdoc/>
+#if NET48
         public Parameters(string parameters) : base(parameters) { }
+#else
+        public Parameters(string? parameters) : base(parameters) { }
+#endif
 
         /// <inheritdoc/>
         public Parameters(RedumpSystem? system, MediaType? type, char driveLetter, string filename, int? driveSpeed, Options options)
@@ -1814,7 +1818,11 @@ namespace MPF.Core.Modules.Aaru
         }
 
         /// <inheritdoc/>
+#if NET48
         protected override bool ValidateAndSetParameters(string parameters)
+#else
+        protected override bool ValidateAndSetParameters(string? parameters)
+#endif
         {
             BaseCommand = CommandStrings.NONE;
 
diff --git a/MPF.Core/Modules/BaseParameters.cs b/MPF.Core/Modules/BaseParameters.cs
index 246488fe..fda68a07 100644
--- a/MPF.Core/Modules/BaseParameters.cs
+++ b/MPF.Core/Modules/BaseParameters.cs
@@ -148,7 +148,11 @@ namespace MPF.Core.Modules
         /// Populate a Parameters object from a param string
         /// </summary>
         /// <param name="parameters">String possibly representing a set of parameters</param>
+#if NET48
         public BaseParameters(string parameters)
+#else
+        public BaseParameters(string? parameters)
+#endif
         {
             // If any parameters are not valid, wipe out everything
             if (!ValidateAndSetParameters(parameters))
@@ -290,7 +294,11 @@ namespace MPF.Core.Modules
         /// </summary>
         /// <param name="parameters">String possibly representing parameters</param>
         /// <returns>True if the parameters were set correctly, false otherwise</returns>
+#if NET48
         protected virtual bool ValidateAndSetParameters(string parameters) => !string.IsNullOrWhiteSpace(parameters);
+#else
+        protected virtual bool ValidateAndSetParameters(string? parameters) => !string.IsNullOrWhiteSpace(parameters);
+#endif
 
         #endregion
 
diff --git a/MPF.Core/Modules/CleanRIp/Parameters.cs b/MPF.Core/Modules/CleanRIp/Parameters.cs
index 42b4b663..e18a56a1 100644
--- a/MPF.Core/Modules/CleanRIp/Parameters.cs
+++ b/MPF.Core/Modules/CleanRIp/Parameters.cs
@@ -22,7 +22,11 @@ namespace MPF.Core.Modules.CleanRip
         #endregion
 
         /// <inheritdoc/>
+#if NET48
         public Parameters(string parameters) : base(parameters) { }
+#else
+        public Parameters(string? parameters) : base(parameters) { }
+#endif
 
         /// <inheritdoc/>
         public Parameters(RedumpSystem? system, MediaType? type, char driveLetter, string filename, int? driveSpeed, Options options)
diff --git a/MPF.Core/Modules/DiscImageCreator/Parameters.cs b/MPF.Core/Modules/DiscImageCreator/Parameters.cs
index 8f0409dc..82ec09c4 100644
--- a/MPF.Core/Modules/DiscImageCreator/Parameters.cs
+++ b/MPF.Core/Modules/DiscImageCreator/Parameters.cs
@@ -187,7 +187,11 @@ namespace MPF.Core.Modules.DiscImageCreator
         #endregion
 
         /// <inheritdoc/>
+#if NET48
         public Parameters(string parameters) : base(parameters) { }
+#else
+        public Parameters(string? parameters) : base(parameters) { }
+#endif
 
         /// <inheritdoc/>
         public Parameters(RedumpSystem? system, MediaType? type, char driveLetter, string filename, int? driveSpeed, Options options)
@@ -2074,7 +2078,11 @@ namespace MPF.Core.Modules.DiscImageCreator
         }
 
         /// <inheritdoc/>
+#if NET48
         protected override bool ValidateAndSetParameters(string parameters)
+#else
+        protected override bool ValidateAndSetParameters(string? parameters)
+#endif
         {
             BaseCommand = CommandStrings.NONE;
 
diff --git a/MPF.Core/Modules/Redumper/Parameters.cs b/MPF.Core/Modules/Redumper/Parameters.cs
index 909d78b0..78534739 100644
--- a/MPF.Core/Modules/Redumper/Parameters.cs
+++ b/MPF.Core/Modules/Redumper/Parameters.cs
@@ -209,7 +209,11 @@ namespace MPF.Core.Modules.Redumper
         #endregion
 
         /// <inheritdoc/>
+#if NET48
         public Parameters(string parameters) : base(parameters) { }
+#else
+        public Parameters(string? parameters) : base(parameters) { }
+#endif
 
         /// <inheritdoc/>
         public Parameters(RedumpSystem? system, MediaType? type, char driveLetter, string filename, int? driveSpeed, Options options)
@@ -1060,7 +1064,11 @@ namespace MPF.Core.Modules.Redumper
         }
 
         /// <inheritdoc/>
+#if NET48
         protected override bool ValidateAndSetParameters(string parameters)
+#else
+        protected override bool ValidateAndSetParameters(string? parameters)
+#endif
         {
             BaseCommand = CommandStrings.NONE;
 
diff --git a/MPF.Core/Modules/UmdImageCreator/Parameters.cs b/MPF.Core/Modules/UmdImageCreator/Parameters.cs
index 9ab584a8..16fd069a 100644
--- a/MPF.Core/Modules/UmdImageCreator/Parameters.cs
+++ b/MPF.Core/Modules/UmdImageCreator/Parameters.cs
@@ -21,7 +21,11 @@ namespace MPF.Core.Modules.UmdImageCreator
         #endregion
 
         /// <inheritdoc/>
+#if NET48
         public Parameters(string parameters) : base(parameters) { }
+#else
+        public Parameters(string? parameters) : base(parameters) { }
+#endif
 
         /// <inheritdoc/>
         public Parameters(RedumpSystem? system, MediaType? type, char driveLetter, string filename, int? driveSpeed, Options options)