diff --git a/DESCRIPTION b/DESCRIPTION
index af2d19b..e502d3b 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: xfun
 Type: Package
 Title: Supporting Functions for Packages Maintained by 'Yihui Xie'
-Version: 0.42.3
+Version: 0.42.4
 Authors@R: c(
   person("Yihui", "Xie", role = c("aut", "cre", "cph"), email = "xie@yihui.name", comment = c(ORCID = "0000-0003-0645-5666")),
   person("Wush", "Wu", role = "ctb"),
diff --git a/R/packages.R b/R/packages.R
index 5459ffc..14fc58f 100644
--- a/R/packages.R
+++ b/R/packages.R
@@ -116,8 +116,11 @@ pkg_require = function(pkgs, which = length(sys.calls()) - 1) {
   )
 }
 
+# update all packages in libraries that are writable by the current user
 pkg_update = function(...) {
-  update.packages(ask = FALSE, checkBuilt = TRUE, ...)
+  libs = .libPaths()
+  libs = libs[file.access(libs, 2) >= 0]
+  for (l in libs) update.packages(l, ask = FALSE, checkBuilt = TRUE, ...)
 }
 
 # allow users to specify a custom install.packages() function via the global