diff --git a/setup_board b/setup_board
index 1e500f4e8f..2596b30157 100755
--- a/setup_board
+++ b/setup_board
@@ -48,9 +48,9 @@ DEFINE_boolean force $FLAGS_FALSE \
   "Force re-creating board root."
 DEFINE_string binutils_version "2.21-r3" \
   "Version of binutils to use."
-DEFINE_string gcc_version "4.6.0-r13" \
+DEFINE_string gcc_version "[stable]" \
   "Version of gcc to use."
-DEFINE_string libc_version "2.11.1-r3" \
+DEFINE_string libc_version "[stable]" \
   "Version of libc to use."
 DEFINE_string kernel_version "3.1" \
   "Version of kernel headers to use."
@@ -134,6 +134,11 @@ toolchain_needs_update() {
 
   # If toolchain symlinks weren't created yet, we definitely need to update.
   if [ ! -d /usr/local/portage/crossdev/cross-$toolchain ]; then
+    # NOTE: In this branch, the versions have not been resolved, and will
+    # be passed directly to crossdev. That works because crossdev understands
+    # '[stable]'.
+    # We cannot resolve the versions because the cross-$toolchain category is
+    # not yet set up.
     return 0
   fi
 
@@ -142,9 +147,23 @@ toolchain_needs_update() {
     return 1
   fi
 
-  # Unmask any ebuilds previously masked by crossdev. crossdev will re-setup
-  # its masks appropriately the next time we run it.
-  sudo rm -f /etc/portage/package.mask/cross-$toolchain
+  # Unmask any ebuilds previously [un]masked by crossdev. crossdev will
+  # re-setup its masks appropriately the next time we run it.
+  sudo rm -f /etc/portage/package.{mask,keywords}/cross-$toolchain
+
+  pkg_to_flag() {
+    [ "${1}" = "glibc" ] && echo "libc" || echo "$1"
+  }
+
+  local pkg
+  for pkg in gcc glibc binutils; do
+    local flagname=FLAGS_$(pkg_to_flag ${pkg})_version
+    if [ "${!flagname}" = "[stable]" ]; then
+      eval ${flagname}=$( \
+          portageq best_visible / "cross-$toolchain/${pkg}"| \
+          sed -e "s,cross-$toolchain/${pkg}-,,")
+    fi
+  done
 
   local flags="--pretend --quiet --update"
   local pkgs
@@ -206,8 +225,11 @@ build_toolchain() {
   if [ $FLAGS_latest_toolchain -ne $FLAGS_TRUE ]; then
     CROSS_ARGS+=" --binutils $FLAGS_binutils_version"
     CROSS_ARGS+=" --gcc $FLAGS_gcc_version"
-    CROSS_ARGS+=" --kernel $FLAGS_kernel_version"
-    CROSS_ARGS+=" --libc $FLAGS_libc_version"
+    if [[ "$toolchain" != "arm-none-eabi" ]]; then
+      # arm-none-eabi needs no version specification
+      CROSS_ARGS+=" --kernel $FLAGS_kernel_version"
+      CROSS_ARGS+=" --libc $FLAGS_libc_version"
+    fi
   fi
 
   CROSS_ARGS+=" --ex-gdb"