diff --git a/.gitignore b/.gitignore
index 170c484..cde0d87 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
 third_party/pkg/
 third_party/src/github.com/kr/
 third_party/src/golang.org/
+
+*.build.log
diff --git a/cross/pkgs/build.json b/cross/pkgs/build.json
index 1d42d16..dc009b1 100644
--- a/cross/pkgs/build.json
+++ b/cross/pkgs/build.json
@@ -1,7 +1,8 @@
 {
 	"CrossCompiledPackages": {
 		"Pre": [
-			"./newlib.sh"
+			"./newlib/build.sh",
+			"./mksh/build.sh"
 		]
 	}
 }
diff --git a/cross/pkgs/mksh/build.sh b/cross/pkgs/mksh/build.sh
new file mode 100755
index 0000000..8820b71
--- /dev/null
+++ b/cross/pkgs/mksh/build.sh
@@ -0,0 +1,84 @@
+#!/bin/bash
+
+# This file is part of Jehanne.
+#
+# Copyright (C) 2017 Giacomo Tesio <giacomo@tesio.it>
+#
+# Jehanne is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 2 of the License.
+#
+# Jehanne is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Jehanne.  If not, see <http://www.gnu.org/licenses/>.
+
+if [ "$JEHANNE" = "" ]; then
+        echo $0 requires the shell started by ./hacking/devshell.sh
+        exit 1
+fi
+
+
+export CROSS_DIR=$JEHANNE/hacking/cross
+export MKSH=$CROSS_DIR/pkgs/mksh/
+export MKSH_SRC=$MKSH/src/
+export MKSH_BUILD=$MKSH/out/
+
+export LD_PRELOAD=
+
+echo -n Building mksh.
+(
+	# Inside parentheses, and therefore a subshell . . .
+	while [ 1 ]   # Endless loop.
+	do
+	  echo -n "."
+	  sleep 3
+	done
+) &
+dotter=$!
+
+cd $MKSH
+
+function failOnError {
+	# $1 -> exit status on a previous command
+	# $2 -> task description
+	if [ $1 -ne 0 ]; then
+		kill $dotter
+		wait $dotter 2>/dev/null
+
+		echo "ERROR $2"
+		if [ "$TRAVIS_BUILD_DIR" != "" ]; then
+			echo
+			cat $MKSH/mksh.build.log
+			echo
+		fi
+		exit $1
+	fi
+}
+
+export TARGET_OS=Jehanne
+export CC=x86_64-jehanne-gcc
+export MKSHRC_PATH='~/lib/mkshrc'
+
+(
+	git clean -xdf . &&
+	mkdir $MKSH_BUILD &&
+	cd $MKSH_BUILD &&
+	sh ../src/Build.sh &&
+	cp mksh $JEHANNE/arch/amd64/cmd/ &&
+	sed -e '3,$s/\bbin\b/cmd/g' ../src/dot.mkshrc > mkshrc &&
+	mkdir -p $JEHANNE/arch/mksh/lib &&
+	cp mkshrc $JEHANNE/arch/mksh/lib &&
+	cp mkshrc $JEHANNE/usr/glenda/lib
+) > $MKSH/mksh.build.log 2>&1
+failOnError $? "building mksh"
+
+
+kill $dotter
+wait $dotter 2>/dev/null
+
+echo "done"
+exit 0;
diff --git a/cross/pkgs/newlib.sh b/cross/pkgs/newlib/build.sh
similarity index 96%
rename from cross/pkgs/newlib.sh
rename to cross/pkgs/newlib/build.sh
index e5fc709..5a90bb7 100755
--- a/cross/pkgs/newlib.sh
+++ b/cross/pkgs/newlib/build.sh
@@ -57,14 +57,14 @@ function failOnError {
 			echo "CONFIG.LOG @ $NEWLIB_BUILD/config.log"
 			echo
 			cat $NEWLIB_BUILD/config.log
-			cat newlib.build.log
+			cat $NEWLIB/newlib.build.log
 		fi
 		exit $1
 	fi
 }
 
 if [ "$NEWLIB_OPTIMIZATION" = "" ]; then
-	NEWLIB_OPTIMIZATION=0
+	NEWLIB_OPTIMIZATION=2
 fi
 
 export CC=gcc
@@ -87,7 +87,7 @@ export CFLAGS_FOR_TARGET="-g -gdwarf-2 -ggdb -O$NEWLIB_OPTIMIZATION"
 	echo "Newlib headers installed at $JEHANNE/sys/posix/newlib/" &&
 	mv $NEWLIB_PREFIX/x86_64-jehanne/lib/ $JEHANNE/arch/amd64/lib/newlib/ &&
 	echo "Newlib libraries installed at $JEHANNE/arch/amd64/lib/newlib/"
-) >> newlib.build.log 2>&1
+) >> $NEWLIB/newlib.build.log 2>&1
 failOnError $? "building newlib"
 
 kill $dotter