--- a/build/autoconf/icu.m4
+++ b/build/autoconf/icu.m4
@@ -144,16 +144,18 @@ if test -z "$BUILDING_JS" -o -n "$JS_STA
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DU_USING_ICU_NAMESPACE=0"
         # don't include obsolete header files
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DU_NO_DEFAULT_INCLUDE_UTF_HEADERS=1"
         # remove chunks of the library that we don't need (yet)
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DUCONFIG_NO_LEGACY_CONVERSION"
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DUCONFIG_NO_TRANSLITERATION"
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DUCONFIG_NO_REGULAR_EXPRESSIONS"
         ICU_CPPFLAGS="$ICU_CPPFLAGS -DUCONFIG_NO_BREAK_ITERATION"
+        # make sure to not accidentally pick up system-icu headers
+        ICU_CPPFLAGS="$ICU_CPPFLAGS -I$icudir/common -I$icudir/i18n"
 
         ICU_CROSS_BUILD_OPT=""
         ICU_SRCDIR=""
         if test "$HOST_OS_ARCH" = "WINNT"; then
     	ICU_SRCDIR="--srcdir=$(cd $srcdir/intl/icu/source; pwd -W)"
         fi
 
         if test "$CROSS_COMPILE"; then