diff --git a/tests/testthat/test.util.R b/tests/testthat/test.util.R
index 6ff632ba..e24aad30 100755
--- a/tests/testthat/test.util.R
+++ b/tests/testthat/test.util.R
@@ -67,7 +67,7 @@ test_that("dlply_ works properly", {
 
 test_that("stop_if_not_installed works properly", {
   e = tryCatch(stop_if_not_installed("_fake_package"), error = function(e) e)
-  expect_s3_class(e, c("ggdist_missing_package"))
-  expect_s3_class(e, c("error"))
+  expect_s3_class(e, "ggdist_missing_package")
+  expect_s3_class(e, "error")
   expect_equal(e$ggdist_package, "_fake_package")
 })
diff --git a/vignettes/slabinterval.Rmd b/vignettes/slabinterval.Rmd
index 9a2a0a2b..ca81258f 100644
--- a/vignettes/slabinterval.Rmd
+++ b/vignettes/slabinterval.Rmd
@@ -361,13 +361,13 @@ p = df %>%
   theme(panel.background = element_rect(color = "grey70"))
 
 (
-  p + stat_slabinterval(side = "left") + 
+  p + stat_slabinterval(side = "left") +
     labs(title = "stat_slabinterval()", subtitle = "side = 'left'")
 ) + (
-  p + stat_slabinterval(side = "both") + 
+  p + stat_slabinterval(side = "both") +
     labs(subtitle = "side = 'both'")
 ) + (
-  p + stat_slabinterval(side = "right")  + 
+  p + stat_slabinterval(side = "right") +
     labs(subtitle = "side = 'right'")
 )
 ```
@@ -384,7 +384,7 @@ p = df %>%
 
 (
   # side = "left" would give the same result
-  p + stat_slabinterval(side = "left") + 
+  p + stat_slabinterval(side = "left") +
     ggtitle("stat_slabinterval()") + labs(subtitle = "side = 'bottom'")
 ) + (
   p + stat_slabinterval(side = "both") + labs(subtitle = "side = 'both'")