diff --git a/bootstrap.sh b/bootstrap.sh
index fd877a644..b0ebcf813 100755
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -1,6 +1,7 @@
 #!/usr/bin/env bash
 
-#set -eu
+set -eu
+set -o pipefail
 
 : '
 
@@ -10,7 +11,7 @@ todo
 - shrink icu data
 '
 
-MASON_VERSION="b709931"
+MASON_VERSION="7ed8931"
 
 function setup_mason() {
     if [[ ! -d ./.mason ]]; then
@@ -33,7 +34,7 @@ function install() {
         if [[ ${3:-false} != false ]]; then
             LA_FILE=$(mason prefix $1 $2)/lib/$3.la
             if [[ -f ${LA_FILE} ]]; then
-               perl -i -p -e 's:\Q$ENV{HOME}/build/mapbox/mason\E:$ENV{PWD}:g' ${LA_FILE}
+                perl -i -p -e 's:\Q$ENV{HOME}/build/mapbox/mason\E:$ENV{PWD}:g' ${LA_FILE}
             else
                 echo "$LA_FILE not found"
             fi
@@ -44,6 +45,7 @@ function install() {
 ICU_VERSION="55.1"
 
 function install_mason_deps() {
+    FAIL=0
     install ccache 3.2.4 &
     install jpeg_turbo 1.4.0 libjpeg &
     install libpng 1.6.20 libpng &
@@ -51,7 +53,6 @@ function install_mason_deps() {
     install libpq 9.4.1 &
     install sqlite 3.8.8.3 libsqlite3 &
     install expat 2.1.0 libexpat &
-    wait
     install icu ${ICU_VERSION} &
     install proj 4.8.0 libproj &
     install pixman 0.32.6 libpixman-1 &
@@ -59,17 +60,22 @@ function install_mason_deps() {
     install protobuf 2.6.1 &
     # technically protobuf is not a mapnik core dep, but installing
     # here by default helps make mapnik-vector-tile builds easier
-    wait
     install webp 0.4.2 libwebp &
     install gdal 1.11.2 libgdal &
     install boost 1.61.0 &
     install boost_libsystem 1.61.0 &
     install boost_libfilesystem 1.61.0 &
     install boost_libprogram_options 1.61.0 &
-    install boost_libregex 1.61.0 &
+    install boost_libregex_icu 1.61.0 &
     install freetype 2.6 libfreetype &
     install harfbuzz 0.9.41 libharfbuzz &
-    wait
+    for job in $(jobs -p)
+    do
+        wait $job || let "FAIL+=1"
+    done
+    if [[ "$FAIL" != "0" ]]; then
+        exit ${FAIL}
+    fi
 }
 
 MASON_LINKED_ABS=$(pwd)/mason_packages/.link
@@ -140,3 +146,8 @@ function main() {
 }
 
 main
+
+# allow sourcing of script without
+# causing the terminal to bail on error
+set +eu
+set +o pipefail
diff --git a/circle.yml b/circle.yml
index cf3e31cb1..a627527a9 100644
--- a/circle.yml
+++ b/circle.yml
@@ -21,7 +21,6 @@ dependencies:
   cache_directories:
     - "~/.ccache"
     - "~/.apt-cache"
-    - "mason_packages"
   pre:
     # https://discuss.circleci.com/t/add-ability-to-cache-apt-get-programs/598/3
     - sudo rm -rf /var/cache/apt/archives && sudo ln -s ~/.apt-cache /var/cache/apt/archives && mkdir -p ~/.apt-cache/partial
diff --git a/src/expression_node.cpp b/src/expression_node.cpp
index 380c36a4e..549f4c891 100644
--- a/src/expression_node.cpp
+++ b/src/expression_node.cpp
@@ -130,9 +130,9 @@ value regex_replace_node::apply(value const& v) const
     auto const& pattern = impl_.get()->pattern_;
     auto const& format = impl_.get()->format_;
 #if defined(BOOST_REGEX_HAS_ICU)
-    return boost::u32regex_replace(v.to_unicode(),pattern,format);
+    return boost::u32regex_replace(v.to_unicode(), pattern, format);
 #else
-    std::string repl = boost::regex_replace(v.to_string(),pattern,format);
+    std::string repl = boost::regex_replace(v.to_string(), pattern, format);
     transcoder tr_("utf8");
     return tr_.transcode(repl.c_str());
 #endif
diff --git a/test/unit/core/expressions_test.cpp b/test/unit/core/expressions_test.cpp
index e60d6127b..c10982f78 100644
--- a/test/unit/core/expressions_test.cpp
+++ b/test/unit/core/expressions_test.cpp
@@ -1,4 +1,3 @@
-
 #include "catch_ext.hpp"
 
 #include <mapnik/expression.hpp>
@@ -176,6 +175,19 @@ TEST_CASE("expressions")
     // regex
     // replace
     TRY_CHECK(eval(" [foo].replace('(\\B)|( )','$1 ') ") == tr.transcode("b a r"));
+
+    // https://en.wikipedia.org/wiki/Chess_symbols_in_Unicode
+    //'\u265C\u265E\u265D\u265B\u265A\u265D\u265E\u265C' - black chess figures
+    // replace black knights with white knights
+    auto val0 = eval(u8"'\u265C\u265E\u265D\u265B\u265A\u265D\u265E\u265C'.replace('\u265E','\u2658')");
+    auto val1 = eval(u8"'♜♞♝♛♚♝♞♜'.replace('♞','♘')"); // ==> expected ♜♘♝♛♚♝♘♜
+    TRY_CHECK(val0 == val1);
+    TRY_CHECK(val0.to_string() == val1.to_string()); // UTF-8
+    TRY_CHECK(val0.to_unicode() == val1.to_unicode()); // Unicode (UTF-16)
+
+    // following test will fail if boost_regex is built without ICU support (unpaired surrogates in output)
+    TRY_CHECK(eval("[name].replace('(\\B)|( )',' ') ") == tr.transcode(u8"Q u é b e c"));
+    TRY_CHECK(eval("'Москва'.replace('(?<!^)(\\B|b)(?!$)',' ')") == tr.transcode(u8"М о с к в а"));
     // 'foo' =~ s:(\w)\1:$1x:r
     TRY_CHECK(eval(" 'foo'.replace('(\\w)\\1', '$1x') ") == tr.transcode("fox"));
     TRY_CHECK(parse_and_dump(" 'foo'.replace('(\\w)\\1', '$1x') ") == "'foo'.replace('(\\w)\\1','$1x')");
@@ -187,8 +199,8 @@ TEST_CASE("expressions")
     TRY_CHECK(parse_and_dump(" [name].match('^Q\\S*$') ") == "[name].match('^Q\\S*$')");
 
     // string & value concatenation
-    // this should evaluate as two strings concatenating, but currently fails
+    // this should evaluate as two strings concatenating
     TRY_CHECK(eval("Hello + '!'") == eval("'Hello!'"));
-    // this should evaulate as a combination of an int value and string, but fails
+    // this should evaulate as a combination of an int value and string
     TRY_CHECK(eval("[int]+m") == eval("'123m'"));
 }