diff --git a/R/build-redirects.R b/R/build-redirects.R
index d61b7cf72..9b43ab232 100644
--- a/R/build-redirects.R
+++ b/R/build-redirects.R
@@ -82,6 +82,9 @@ reference_redirects <- function(pkg) {
 
   names(redirects) <- paste0(names(redirects), ".html")
 
+  # Ensure we don't create an invalid file name
+  redirects <- redirects[grepl("^[a-zA-Z0-9._-]+$", names(redirects))]
+
   # Ensure we don't override an existing file
   redirects <- redirects[setdiff(names(redirects), pkg$topics$file_out)]
 
diff --git a/tests/testthat/test-build-redirects.R b/tests/testthat/test-build-redirects.R
index 5b254cd70..ddc8bc87d 100644
--- a/tests/testthat/test-build-redirects.R
+++ b/tests/testthat/test-build-redirects.R
@@ -63,6 +63,21 @@ test_that("generates redirects only for non-name aliases", {
   )
 })
 
+test_that("doesn't generates redirect for aliases that can't be file names", {
+  pkg <- list(
+    meta = list(url = "http://foo.com"),
+    topics = list(
+      name = "bar",
+      alias = list(c("bar", "baz", "[<-.baz")),
+      file_out = "bar.html"
+    )
+  )
+  expect_equal(
+    reference_redirects(pkg),
+    list(c("reference/baz.html", "reference/bar.html"))
+  )
+})
+
 test_that("never redirects away from existing topic", {
   pkg <- list(
     meta = list(url = "http://foo.com"),
@@ -89,4 +104,3 @@ test_that("no redirects if no aliases", {
   )
   expect_equal(reference_redirects(pkg), list())
 })
-
diff --git a/tests/testthat/test-build-search-docs.R b/tests/testthat/test-build-search-docs.R
index fa2edeee9..d9432c482 100644
--- a/tests/testthat/test-build-search-docs.R
+++ b/tests/testthat/test-build-search-docs.R
@@ -66,14 +66,6 @@ test_that("build_search() builds the expected search.json with no URL", {
   expect_snapshot_file(json_path, "search-no-url.json")
 })
 
-test_that("build_sitemap() handles special xml characters", {
-  pkg <- local_pkgdown_site()
-  file_create(path(pkg$dst_path, "[<-.foo.html"))
-
-  suppressMessages(build_sitemap(pkg))
-  expect_no_error(xml2::read_xml(path(pkg$dst_path, "sitemap.xml")))
-})
-
 test_that("sitemap excludes redirects", {
   pkg <- local_pkgdown_site(meta = list(
     url = "https://example.com",