diff --git a/tests/reg-tests-1e.R b/tests/reg-tests-1e.R
index 9c7790a829a..faab3692163 100644
--- a/tests/reg-tests-1e.R
+++ b/tests/reg-tests-1e.R
@@ -1399,6 +1399,11 @@ ch0 <- character(0L)
 stopifnot(identical(ch0, tools::toTitleCase(ch0)))
 ## was list() in R <= 4.4.0
 
+## toTitleCase("'PROTECTED',")
+stopifnot(identical(
+  tools::toTitleCase("'SPSS', 'Stata' and 'R' are statistical software"),
+  tools::toTitleCase("'SPSS' 'Stata' and 'R' are statistical software")
+))
 
 ## PR#18745 (+ PR#18702)   format.data.frame() -> as.data.frame.list()
 x <- setNames(data.frame(TRUE), NA_character_)