diff --git a/bin/polynum-build-virtualenv b/bin/polynum-build-virtualenv
index 3ca07f8..3cd8395 100755
--- a/bin/polynum-build-virtualenv
+++ b/bin/polynum-build-virtualenv
@@ -1,7 +1,27 @@
 #!/bin/bash
 
+# search Python version and python executable
+PYTHON_EXE=`which python2.6` || exit 1
+
+# search virtualenv executable and check its version
+for VIRTUALENV_SUFFIX in "-2.7" "-2.6" ""
+do
+	VIRTUALENV_EXE=`which virtualenv$VIRTUALENV_SUFFIX 2> /dev/null` && break
+done
+
+VIRTUALENV_VERSION=$((`$VIRTUALENV_EXE --version | sed 's/^\([0-9]\+\)\.\([0-9]\+\)\..*/\1*1000+\2/'`))
+if [ "$VIRTUALENV_VERSION" -ge 1007 ]
+then
+	VIRTUALENV_OPTS=--system-site-packages
+fi
+
+# where are requirements ? (deb and rpm don't use same doc directory)
+REQUIREMENTS=`ls -1 /usr/share/doc/polynum*/requirements | sort -r | head -1`
+
+# where to build the virtualenv : /opt/polynum/virtualenv by defaut
 VEDIR=${VIRTUAL_ENV-/opt/polynum/virtualenv}
 
+# pip can use a --proxy option
 PIPOPT=$PIPOPT" --log=$VEDIR/install.log"
 if [ x"$PROXY" != "x" ]; then
   PIPOPT=$PIPOPT" --proxy=$PROXY"
@@ -21,20 +41,24 @@ test -d $DIR || "$DIR does not exist (or is not a directory)"
 cd $DIR || abort "cannot cd to $DIR"
 
 echo ""
-echo "Building PolyNum virtualenv in $VEDIR"
-echo "(detailed log in $VEDIR/install.log)"
+echo "Building PolyNum virtualenv in $VEDIR :"
+echo "  $VIRTUALENV_EXE --python=${PYTHON_EXE} $VIRTUALENV_OPTS $VE"
 echo ""
 
-virtualenv --system-site-packages $VE || abort "cannot create virtualenv $VE in $DIR"
+$VIRTUALENV_EXE --python=${PYTHON_EXE} $VIRTUALENV_OPTS $VE || abort "cannot create virtualenv $VE in $DIR"
 
 cd $VE
 . bin/activate || abort "cannot activate virtualenv (???)"
+
+echo ""
+echo "Installing packages with pip (detailed log in $VEDIR/install.log)"
+echo ""
 pip $PIPOPT install -U pip
-pip $PIPOPT install --requirement=/usr/share/doc/polynum/requirements
+pip $PIPOPT install --requirement=$REQUIREMENTS
 
 echo ""
 echo -n "Creating .pyc files (compileall) .."
-python -m compileall -f -q $VEDIR
+$PYTHON_EXE -m compileall -f -q $VEDIR
 echo "..done"
 
 echo ""
diff --git a/bin/polynum-manage.py b/bin/polynum-manage.py
index 0ca83a3..a5abc0e 100755
--- a/bin/polynum-manage.py
+++ b/bin/polynum-manage.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2.6
 import os
 import sys
 import site