diff --git a/DESCRIPTION b/DESCRIPTION
index cf68f64..b6c8d41 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: auditor
 Title: Model Audit - Verification, Validation, and Error Analysis 
-Version: 1.3.4
+Version: 1.3.5
 Authors@R: c(
     person("Alicja", "Gosiewska", email = "alicjagosiewska@gmail.com", role = c("aut", "cre"),
       comment = c(ORCID = "0000-0001-6563-5742")),
@@ -10,7 +10,8 @@ Authors@R: c(
       comment = c(ORCID = "0000-0001-6661-5364")),
     person("Tomasz", "Mikołajczyk", role =  c("aut")),
     person("Michal", "Burdukiewicz", role =  c("ctb")),
-    person("Szymon", "Maksymiuk", role =  c("ctb"))
+    person("Szymon", "Maksymiuk", role =  c("ctb")),
+    person("Michal", "Kaminski", role =  c("ctb"))
   )
 Description: Provides an easy to use unified interface for creating validation plots for any model. 
   The 'auditor' helps to avoid repetitive work consisting of writing code needed to create residual plots. 
diff --git a/R/plot_acf.R b/R/plot_acf.R
index 76a7886..f7ac42f 100644
--- a/R/plot_acf.R
+++ b/R/plot_acf.R
@@ -51,11 +51,15 @@ plot_acf <- function(object, ..., variable = NULL, alpha = 0.95) {
   # data frame for ggplot object
   df <- make_dataframe(object, ..., variable = variable, type = "res")
 
-  result_df <- data.frame(acf = numeric(), label = character(), lag = numeric(), ymin = numeric())
-  for (label in unique(df$`_label_`)) {
+
+  result_df <- data.frame(acf = numeric(), label = factor(), lag = numeric(), ymin = numeric())
+
+  label_levels <- levels(df$`_label_`)
+
+  for (label in label_levels) {
     orderedResiduals <- df[which(df$`_label_` == label), "_residuals_"]
     acf <- acf(orderedResiduals, plot = FALSE)
-    result_df <- rbind(result_df, data.frame(acf = acf$acf[-1], label = label, lag = acf$lag[-1], ymin = 0))
+    result_df <- rbind(result_df, data.frame(acf = acf$acf[-1], label = factor(label, levels = label_levels), lag = acf$lag[-1], ymin = 0))
   }
 
   df <- result_df
diff --git a/tests/testthat/objects_for_tests.R b/tests/testthat/objects_for_tests.R
index 819baa9..b64af2e 100644
--- a/tests/testthat/objects_for_tests.R
+++ b/tests/testthat/objects_for_tests.R
@@ -45,11 +45,13 @@ model_class_glm2 <- glm(factor(y) ~ x3, family=binomial,	data=artifficial_classi
 exp_class_glm2 <- explain(model_class_glm2, data = artifficial_classif, y = artifficial_classif$y, verbose = FALSE)
 exp_lm <- explain(model_lm, label = "lm", data = artifficial_regr, y = artifficial_regr$y, verbose = FALSE)
 exp_glm <- explain(model_glm, label = "glm", data = artifficial_classif_2, y = artifficial_classif_2$y, verbose = FALSE)
+exp_glm2 <- explain(model_glm, label = "glm2", data = artifficial_classif_2, y = artifficial_classif_2$y, verbose = FALSE)
 exp_rf <- explain(model_rf, label="rf", data =artifficial_classif_2, y = artifficial_classif_2$y, verbose = FALSE)
 exp_class_glm <- explain(model_class_glm, label="class glm", data = artifficial_classif, y = artifficial_classif$y, verbose = FALSE)
 
 mr_rf <- model_residual(exp_rf)
 mr_glm <- model_residual(exp_glm)
+mr_glm2 <- model_residual(exp_glm2)
 
 cd_lm <- model_cooksdistance(exp_lm)
 cd_rf <- model_cooksdistance(exp_rf)
diff --git a/tests/testthat/test_plotsR.R b/tests/testthat/test_plotsR.R
index 4a7cde9..d5e4483 100644
--- a/tests/testthat/test_plotsR.R
+++ b/tests/testthat/test_plotsR.R
@@ -7,6 +7,7 @@ test_that("plot_acf", {
   expect_is(plot_acf(mr_rf, variable = "_y_"), "gg")
   expect_is(plot_acf(mr_rf, variable = "_y_hat_"), "gg")
   expect_is(plot_acf(mr_rf), "gg")
+  expect_error(plot_acf(mr_rf, mr_glm, mr_glm2), NA)
 })
 
 test_that("plot_autocorrelation", {