diff --git a/pkgs/by-name/da/dafny/package.nix b/pkgs/by-name/da/dafny/package.nix
index 54f88b7b36c6..6ff063fdc4b5 100644
--- a/pkgs/by-name/da/dafny/package.nix
+++ b/pkgs/by-name/da/dafny/package.nix
@@ -65,11 +65,18 @@ buildDotnetModule rec {
       # frameworks, you must specify the framework for the published
       # application."
       substituteInPlace Source/DafnyRuntime/DafnyRuntime.csproj \
-        --replace-warn TargetFrameworks TargetFramework \
-        --replace-warn "netstandard2.0;net452" net6.0
+        --replace-fail TargetFrameworks TargetFramework \
+        --replace-fail "netstandard2.0;net452" net8.0
+
+      for f in Source/**/*.csproj ; do
+        [[ "$f" == "Source/DafnyRuntime/DafnyRuntime.csproj" ]] && continue;
+
+        substituteInPlace $f \
+          --replace-fail net6.0 net8.0
+      done
     '';
 
-  dotnet-sdk = dotnetCorePackages.sdk_6_0;
+  dotnet-sdk = dotnetCorePackages.sdk_8_0;
   nativeBuildInputs = [ jdk11 ];
   nugetDeps = ./deps.json;