diff --git a/pkgs/by-name/om/omnisharp-roslyn/deps.nix b/pkgs/by-name/om/omnisharp-roslyn/deps.nix
index 65912a50593b8..2d8a19ef1be6a 100644
--- a/pkgs/by-name/om/omnisharp-roslyn/deps.nix
+++ b/pkgs/by-name/om/omnisharp-roslyn/deps.nix
@@ -11,6 +11,7 @@
   (fetchNuGet { pname = "ICSharpCode.Decompiler"; version = "8.2.0.7535"; hash = "sha256-4BWs04Va9pc/SLeMA/vKoBydhw+Bu6s9MDtoo/Ucft8="; })
   (fetchNuGet { pname = "McMaster.Extensions.CommandLineUtils"; version = "4.1.0"; hash = "sha256-lPAL8r1/y6WmWpgKqYHzIa3iEz1+Soqkud4XnbpN/N4="; })
   (fetchNuGet { pname = "MediatR"; version = "8.1.0"; hash = "sha256-dyqhDG1NJjY1b+dj37sMmklGkxAm3zKdhh2lBJ0/HTM="; })
+  (fetchNuGet { pname = "Microsoft.AspNetCore.App.Ref"; version = "6.0.36"; hash = "sha256-9jDkWbjw/nd8yqdzVTagCuqr6owJ/DUMi4BlUZT4hWU="; })
   (fetchNuGet { pname = "Microsoft.Bcl.AsyncInterfaces"; version = "7.0.0"; hash = "sha256-1e031E26iraIqun84ad0fCIR4MJZ1hcQo4yFN+B7UfE="; })
   (fetchNuGet { pname = "Microsoft.Bcl.AsyncInterfaces"; version = "8.0.0"; hash = "sha256-9aWmiwMJKrKr9ohD1KSuol37y+jdDxPGJct3m2/Bknw="; })
   (fetchNuGet { pname = "Microsoft.Build"; version = "17.3.2"; hash = "sha256-r+jLFj4SFlkcRofhbt4/8IzA4mYnDlfv2IkiwYCa5J0="; })
@@ -60,6 +61,7 @@
   (fetchNuGet { pname = "Microsoft.Extensions.Primitives"; version = "8.0.0"; hash = "sha256-FU8qj3DR8bDdc1c+WeGZx/PCZeqqndweZM9epcpXjSo="; })
   (fetchNuGet { pname = "Microsoft.IO.Redist"; version = "6.0.0"; hash = "sha256-pa3MT+QWrWeehQwUWtTS/Rwto8IIDgAt+zLqaUAQoJ0="; })
   (fetchNuGet { pname = "Microsoft.NET.StringTools"; version = "17.3.2"; hash = "sha256-Q8owHXaXkJPy13yGlj+VYGS9XMqYWUZYB6yoT0/m4ek="; })
+  (fetchNuGet { pname = "Microsoft.NETCore.App.Ref"; version = "6.0.36"; hash = "sha256-9LZgVoIFF8qNyUu8kdJrYGLutMF/cL2K82HN2ywwlx8="; })
   (fetchNuGet { pname = "Microsoft.NETCore.Platforms"; version = "1.1.0"; hash = "sha256-FeM40ktcObQJk4nMYShB61H/E8B7tIKfl9ObJ0IOcCM="; })
   (fetchNuGet { pname = "Microsoft.NETCore.Platforms"; version = "5.0.0"; hash = "sha256-LIcg1StDcQLPOABp4JRXIs837d7z0ia6+++3SF3jl1c="; })
   (fetchNuGet { pname = "Microsoft.NETFramework.ReferenceAssemblies"; version = "1.0.3"; hash = "sha256-FBoJP5DHZF0QHM0xLm9yd4HJZVQOuSpSKA+VQRpphEE="; })
@@ -108,6 +110,7 @@
   (fetchNuGet { pname = "System.Configuration.ConfigurationManager"; version = "8.0.0"; hash = "sha256-xhljqSkNQk8DMkEOBSYnn9lzCSEDDq4yO910itptqiE="; })
   (fetchNuGet { pname = "System.Data.DataSetExtensions"; version = "4.5.0"; hash = "sha256-qppO0L8BpI7cgaStqBhn6YJYFjFdSwpXlRih0XFsaT4="; })
   (fetchNuGet { pname = "System.Diagnostics.DiagnosticSource"; version = "8.0.0"; hash = "sha256-+aODaDEQMqla5RYZeq0Lh66j+xkPYxykrVvSCmJQ+Vs="; })
+  (fetchNuGet { pname = "System.Diagnostics.EventLog"; version = "8.0.0"; hash = "sha256-rt8xc3kddpQY4HEdghlBeOK4gdw5yIj4mcZhAVtk2/Y="; })
   (fetchNuGet { pname = "System.Drawing.Common"; version = "6.0.0"; hash = "sha256-/9EaAbEeOjELRSMZaImS1O8FmUe8j4WuFUw1VOrPyAo="; })
   (fetchNuGet { pname = "System.Formats.Asn1"; version = "6.0.0"; hash = "sha256-KaMHgIRBF7Nf3VwOo+gJS1DcD+41cJDPWFh+TDQ8ee8="; })
   (fetchNuGet { pname = "System.IO.Pipelines"; version = "7.0.0"; hash = "sha256-W2181khfJUTxLqhuAVRhCa52xZ3+ePGOLIPwEN8WisY="; })
diff --git a/pkgs/by-name/om/omnisharp-roslyn/package.nix b/pkgs/by-name/om/omnisharp-roslyn/package.nix
index 5ca7c3290eab0..04b310d5d7a25 100644
--- a/pkgs/by-name/om/omnisharp-roslyn/package.nix
+++ b/pkgs/by-name/om/omnisharp-roslyn/package.nix
@@ -3,13 +3,12 @@
   dotnetCorePackages,
   fetchFromGitHub,
   lib,
-  stdenv,
   runCommand,
   expect,
 }:
 
 let
-  inherit (dotnetCorePackages) sdk_8_0 runtime_6_0;
+  inherit (dotnetCorePackages) sdk_8_0 sdk_9_0 runtime_8_0;
 in
 let
   finalPackage = buildDotnetModule rec {
@@ -26,17 +25,12 @@ let
     projectFile = "src/OmniSharp.Stdio.Driver/OmniSharp.Stdio.Driver.csproj";
     nugetDeps = ./deps.nix;
 
-    dotnet-sdk =
-      with dotnetCorePackages;
-      combinePackages [
-        sdk_6_0
-        sdk_8_0
-      ];
+    dotnet-sdk = sdk_8_0;
     dotnet-runtime = sdk_8_0;
 
-    dotnetInstallFlags = [ "--framework net6.0" ];
+    dotnetInstallFlags = [ "--framework net8.0" ];
     dotnetBuildFlags = [
-      "--framework net6.0"
+      "--framework net8.0"
       "--no-self-contained"
     ];
     dotnetFlags = [
@@ -45,7 +39,7 @@ let
       "-property:AssemblyVersion=${version}.0"
       "-property:FileVersion=${version}.0"
       "-property:InformationalVersion=${version}"
-      "-property:RuntimeFrameworkVersion=${runtime_6_0.version}"
+      "-property:RuntimeFrameworkVersion=${runtime_8_0.version}"
       "-property:RollForward=LatestMajor"
     ];
 
@@ -56,8 +50,11 @@ let
       # Patch the project files so we can compile them properly
       for project in src/OmniSharp.Http.Driver/OmniSharp.Http.Driver.csproj src/OmniSharp.LanguageServerProtocol/OmniSharp.LanguageServerProtocol.csproj src/OmniSharp.Stdio.Driver/OmniSharp.Stdio.Driver.csproj; do
         substituteInPlace $project \
-          --replace '<RuntimeIdentifiers>win7-x64;win7-x86;win10-arm64</RuntimeIdentifiers>' '<RuntimeIdentifiers>linux-x64;linux-arm64;osx-x64;osx-arm64</RuntimeIdentifiers>'
+          --replace-fail '<RuntimeIdentifiers>win7-x64;win7-x86;win10-arm64</RuntimeIdentifiers>' '<RuntimeIdentifiers>linux-x64;linux-arm64;osx-x64;osx-arm64</RuntimeIdentifiers>'
       done
+      substituteInPlace src/OmniSharp.Stdio.Driver/OmniSharp.Stdio.Driver.csproj \
+        --replace-fail 'net6.0' 'net8.0' \
+        --replace-fail '<RuntimeFrameworkVersion>6.0.0-preview.7.21317.1</RuntimeFrameworkVersion>' ""
     '';
 
     useDotnetFromEnv = true;
@@ -96,8 +93,8 @@ let
       in
       {
         # Make sure we can run OmniSharp with any supported SDK version, as well as without
-        with-net6-sdk = with-sdk dotnetCorePackages.sdk_6_0;
-        with-net8-sdk = with-sdk dotnetCorePackages.sdk_8_0;
+        with-net8-sdk = with-sdk sdk_8_0;
+        with-net9-sdk = with-sdk sdk_9_0;
         no-sdk = with-sdk null;
       };