diff --git a/tests/testthat/test-io.R b/tests/testthat/test-io.R
index 6195fd52d..89fca4dff 100644
--- a/tests/testthat/test-io.R
+++ b/tests/testthat/test-io.R
@@ -6,8 +6,10 @@ test_that("non-ASCII characters are handled properly for text styling", {
 
 
 test_that("non-ASCII characters are handled properly for file styling", {
-  skip_if(.Platform$OS.type != "windows")
-
+  # to avoid warnings
+  #  on unix: 'OS reports request to set locale to "English_United States.1252" cannot be honored'
+  #  on win: 'using locale code page other than 65001 ("UTF-8") may cause problems'
+  withr::local_options(list(warn = -1L))
   withr::with_locale(
     c(LC_CTYPE = "English_United States.1252"),
     {
diff --git a/tests/testthat/tests-cache-require-serial.R b/tests/testthat/tests-cache-require-serial.R
index ae7226b3c..ca0807866 100644
--- a/tests/testthat/tests-cache-require-serial.R
+++ b/tests/testthat/tests-cache-require-serial.R
@@ -25,7 +25,7 @@ test_that("top-level test: Caches top-level expressions efficiently on style_tex
     partially_cached_benchmark["elapsed"] * 1.5,
     not_cached_benchmark["elapsed"]
   )
-  expect_lt(full_cached_benchmark["elapsed"] * 30, benchmark["elapsed"])
+  expect_lt(full_cached_benchmark["elapsed"] * 20, benchmark["elapsed"])
 })