diff --git a/R/calc_TLLxTxRatio.R b/R/calc_TLLxTxRatio.R
index 232fd1775..2f70a8947 100644
--- a/R/calc_TLLxTxRatio.R
+++ b/R/calc_TLLxTxRatio.R
@@ -149,6 +149,7 @@ calc_TLLxTxRatio <- function(
 # Calculate Lx/Tx values --------------------------------------------------
     ## preset variables
     net_LnLx <- net_LnLx.Error <- net_TnTx <- net_TnTx.Error <- NA
+    BG.Error <- NA
 
     ## calculate values
     LnLx <- sum(Lx.data.signal[signal.integral.min:signal.integral.max, 2])
diff --git a/tests/testthat/test_calc_TLLxTxRatio.R b/tests/testthat/test_calc_TLLxTxRatio.R
index 1a77acaea..cab4ac9b5 100644
--- a/tests/testthat/test_calc_TLLxTxRatio.R
+++ b/tests/testthat/test_calc_TLLxTxRatio.R
@@ -102,4 +102,11 @@ test_that("calc_TLLxTxRatio", {
   expect_equal(round(results$LxTx, digits =  6), 3.187877)
   expect_equal(round(results$LxTx.Error, digits = 6), 1.485073)
 
+  expect_s4_class(calc_TLLxTxRatio(
+    Lx.data.signal,
+    Lx.data.background=NULL,
+    Tx.data.signal,
+    Tx.data.background=NULL,
+    signal.integral.min,
+    signal.integral.max), class = "RLum.Results")
 })