diff --git a/pkgs/build-support/dotnetenv/build-solution.nix b/pkgs/build-support/dotnetenv/build-solution.nix
index 495f2f116ea4..65e4ca71475b 100644
--- a/pkgs/build-support/dotnetenv/build-solution.nix
+++ b/pkgs/build-support/dotnetenv/build-solution.nix
@@ -42,7 +42,7 @@ stdenv.mkDerivation {
     fi
     
     ensureDir $out
-    MSBuild.exe ${slnFile} /nologo /t:${targets} /p:IntermediateOutputPath=$(cygpath --windows $out)\\ /p:OutputPath=$(cygpath --windows $out)\\ /verbosity:${verbosity} ${options}
+    MSBuild.exe ${toString slnFile} /nologo /t:${targets} /p:IntermediateOutputPath=$(cygpath --windows $out)\\ /p:OutputPath=$(cygpath --windows $out)\\ /verbosity:${verbosity} ${options}
     
     # Create references to runtime dependencies
     # !!! Should be more efficient (e.g. symlinking)