diff --git a/INSTALL.md b/INSTALL.md
index b701a7dc9..4ef4a2124 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -184,7 +184,7 @@ If you need help or want to participate starting points include:
 ### Cartographers
 
 TileMill, which uses Mapnik internally, offers great step by step tutorials for
-learning advanced map styling: http://mapbox.com/tilemill/docs/crashcourse/introduction/
+learning advanced map styling: https://tilemill-project.github.io/tilemill/docs/crashcourse/introduction/
 
 ### Programmers
 
diff --git a/bootstrap.sh b/bootstrap.sh
index 24706b8be..583b83fe6 100755
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -8,7 +8,7 @@ todo
 - shrink icu data
 '
 
-MASON_VERSION="cce4ebf4"
+MASON_VERSION="fde1d9f5"
 
 function setup_mason() {
     if [[ ! -d ./.mason ]]; then
@@ -43,7 +43,7 @@ function install() {
     mason link $1 $2
 }
 
-ICU_VERSION="57.1"
+ICU_VERSION="58.1"
 BOOST_VERSION="1.74.0"
 
 function install_mason_deps() {
@@ -65,7 +65,7 @@ function install_mason_deps() {
     install boost_libsystem ${BOOST_VERSION}
     install boost_libfilesystem ${BOOST_VERSION}
     install boost_libprogram_options ${BOOST_VERSION}
-    install boost_libregex_icu57 ${BOOST_VERSION}
+    install boost_libregex_icu58 ${BOOST_VERSION}
     # technically boost thread and python are not a core dep, but installing
     # here by default helps make python-mapnik builds easier
     install boost_libthread ${BOOST_VERSION}