diff --git a/Directory.Build.props b/Directory.Build.props
index a16683b..0fd6b4f 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -7,7 +7,7 @@
              JasperFx.Events, JasperFx.Events.SourceGenerator) set
              <Version>$(JasperFxVersion)</Version> so they always release together. Bump this one
              value to release the whole set. -->
-        <JasperFxVersion>2.1.2</JasperFxVersion>
+        <JasperFxVersion>2.1.3</JasperFxVersion>
         <LangVersion>13</LangVersion>
         <NoWarn>1570;1571;1572;1573;1574;1587;1591;1701;1702;1711;1735;0618</NoWarn>
         <Authors>Jeremy D. Miller;Jaedyn Tonee</Authors>
diff --git a/src/JasperFx.SourceGenerator.Tests/InputParserGeneratorTests.cs b/src/JasperFx.SourceGenerator.Tests/InputParserGeneratorTests.cs
new file mode 100644
index 0000000..5da0eec
--- /dev/null
+++ b/src/JasperFx.SourceGenerator.Tests/InputParserGeneratorTests.cs
@@ -0,0 +1,71 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using JasperFx;
+using JasperFx.SourceGenerator;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Shouldly;
+
+namespace JasperFx.SourceGenerator.Tests;
+
+// GH-378: the generated input parser cast a Dictionary<string, string?> flag (e.g. the inherited
+// NetCoreInput.ConfigFlag) to IDictionary<string, string>, which is CS8619 under
+// `#nullable enable` + TreatWarningsAsErrors and broke consumer builds (notably net10 — Wolverine).
+public class InputParserGeneratorTests
+{
+    private const string Source = """
+        using System.Collections.Generic;
+        using JasperFx.CommandLine;
+
+        namespace App;
+
+        public class SampleInput
+        {
+            // Mirrors the inherited NetCoreInput.ConfigFlag that broke the Wolverine build.
+            public Dictionary<string, string?> ConfigFlag = new();
+        }
+
+        public class SampleCommand : JasperFxCommand<SampleInput>
+        {
+            public override bool Execute(SampleInput input) => true;
+        }
+        """;
+
+    private static (string? parser, IEnumerable<Diagnostic> diagnostics) Run()
+    {
+        var tree = CSharpSyntaxTree.ParseText(Source);
+        var runtimeDir = Path.GetDirectoryName(typeof(object).Assembly.Location)!;
+        var references = new List<MetadataReference>
+        {
+            MetadataReference.CreateFromFile(typeof(object).Assembly.Location),
+            MetadataReference.CreateFromFile(typeof(IJasperFxExtension).Assembly.Location),
+            MetadataReference.CreateFromFile(Path.Combine(runtimeDir, "System.Runtime.dll")),
+            MetadataReference.CreateFromFile(Path.Combine(runtimeDir, "System.Collections.dll")),
+        };
+
+        // Nullable enabled so the CS8619 nullability mismatch would surface if it regressed.
+        var compilation = CSharpCompilation.Create("TestAssembly", [tree], references,
+            new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary,
+                nullableContextOptions: NullableContextOptions.Enable));
+
+        GeneratorDriver driver = CSharpGeneratorDriver.Create(new InputParserGenerator());
+        driver = driver.RunGeneratorsAndUpdateCompilation(compilation, out var output, out _);
+
+        var parser = driver.GetRunResult().GeneratedTrees
+            .Select(t => t.GetText().ToString())
+            .FirstOrDefault(t => t.Contains("SampleInputParser"));
+
+        return (parser, output.GetDiagnostics());
+    }
+
+    [Fact]
+    public void dictionary_flag_parser_compiles_clean_under_nullable()
+    {
+        var (parser, diagnostics) = Run();
+
+        parser.ShouldNotBeNull("The InputParserGenerator should have produced a parser for SampleInput");
+        parser.ShouldContain("#nullable disable");
+        diagnostics.Where(d => d.Id == "CS8619").ShouldBeEmpty();
+    }
+}
diff --git a/src/JasperFx.SourceGenerator/InputParserGenerator.cs b/src/JasperFx.SourceGenerator/InputParserGenerator.cs
index f77b403..f7fa43b 100644
--- a/src/JasperFx.SourceGenerator/InputParserGenerator.cs
+++ b/src/JasperFx.SourceGenerator/InputParserGenerator.cs
@@ -451,7 +451,13 @@ private static void GenerateParserClass(SourceProductionContext context, InputMo
     {
         var sb = new StringBuilder();
         sb.AppendLine("// <auto-generated />");
-        sb.AppendLine("#nullable enable");
+        // Disable nullable analysis in the generated parser. It casts input flag members to the
+        // delegate types that GeneratedDictionaryFlag/GeneratedFlag expect (e.g. IDictionary<string,
+        // string>), which are runtime-identical to but nullably-distinct from members declared as
+        // Dictionary<string, string?> (such as the inherited NetCoreInput.ConfigFlag). Under
+        // `#nullable enable` + TreatWarningsAsErrors that mismatch is CS8619 and breaks the consumer
+        // build (notably net10). Generated code shouldn't participate in nullable analysis. See GH-378.
+        sb.AppendLine("#nullable disable");
         sb.AppendLine("using System;");
         sb.AppendLine("using System.Collections.Generic;");
         sb.AppendLine("using JasperFx.CommandLine.Parsing;");