diff --git a/tools/tht/internal/safeio/private_windows_test.go b/tools/tht/internal/safeio/private_windows_test.go
index 84e66845..8b238614 100644
--- a/tools/tht/internal/safeio/private_windows_test.go
+++ b/tools/tht/internal/safeio/private_windows_test.go
@@ -342,7 +342,28 @@ func TestCreateCanonicalNewPrivateFileInstallsOwnerOnlyDACLAtCreation(t *testing
 	}
 	defer file.Close()
 	if err := ValidatePrivateRegular(path); err != nil {
-		t.Fatalf("new lock DACL error = %v", err)
+		parents, target, parentErr := openCanonicalWindowsParent(path)
+		if parentErr != nil {
+			t.Fatalf("new lock DACL error = %T %v; raw parent open = %T %v", err, err, parentErr, parentErr)
+		}
+		defer parents.Close()
+		handle, openErr := openWindowsRelativeObject(
+			parents.handles[len(parents.handles)-1],
+			target,
+			windows.GENERIC_READ,
+			windows.FILE_OPEN,
+			windows.FILE_NON_DIRECTORY_FILE|windows.FILE_SYNCHRONOUS_IO_NONALERT|windows.FILE_OPEN_REPARSE_POINT,
+			nil,
+		)
+		if openErr != nil {
+			t.Fatalf("new lock DACL error = %T %v; raw regular open = %T %v", err, err, openErr, openErr)
+		}
+		defer windows.CloseHandle(handle)
+		var info windows.ByHandleFileInformation
+		infoErr := windows.GetFileInformationByHandle(handle, &info)
+		daclErr := validateOwnerOnlyDACL(handle)
+		t.Fatalf("new lock DACL error = %T %v; raw info = %T %v attributes=%#x links=%d; raw dacl = %T %v",
+			err, err, infoErr, infoErr, info.FileAttributes, info.NumberOfLinks, daclErr, daclErr)
 	}
 }