diff --git a/configure b/configure
index baeae947..c32420a0 100755
--- a/configure
+++ b/configure
@@ -480,11 +480,15 @@ def create_ninja_and_rc(l_installed):
         'export QP_PYTHON={0}'.format(":".join(l_python)), "",
         'export IRPF90={0}'.format(path_irpf90.replace(QP_ROOT,"${QP_ROOT}")),
         'export NINJA={0}'.format(path_ninja.replace(QP_ROOT,"${QP_ROOT}")),
-        'export PYTHONPATH="${QP_EZFIO}/Python":"${QP_PYTHON}":"${PYTHONPATH}"',
-        'export PATH="${QP_PYTHON}":"${QP_ROOT}"/bin:"${QP_ROOT}"/ocaml:"${PATH}"',
-        'export LD_LIBRARY_PATH="${QP_ROOT}"/lib:"${QP_ROOT}"/lib64:"${LD_LIBRARY_PATH}"',
-        'export LIBRARY_PATH="${QP_ROOT}"/lib:"${QP_ROOT}"/lib64:"${LIBRARY_PATH}"',
-        'export C_INCLUDE_PATH="${C_INCLUDE_PATH}":"${QP_ROOT}"/include',
+        'qp_append_export () {',
+        '   #Append path $2:${!1}. Add the semicolon only if ${!1} is defined',
+        '   echo ${2}${!1:+:${!1}}',
+        '}',
+        'export PYTHONPATH=$(qp_append_export "PYTHONPATH" "${QP_EZFIO}/Python":"${QP_PYTHON}")',
+        'export PATH=$(qp_append_export "PATH" "${QP_PYTHON}":"${QP_ROOT}"/bin:"${QP_ROOT}"/ocaml)',
+        'export LD_LIBRARY_PATH=$(qp_append_export "LD_LIBRARY_PATH" "${QP_ROOT}"/lib:"${QP_ROOT}"/lib64)',
+        'export LIBRARY_PATH=$(qp_append_export "LIBRARY_PATH" "${QP_ROOT}"/lib:"${QP_ROOT}"/lib64)',
+        'export C_INCLUDE_PATH=$(qp_append_export "C_INCLUDE_PATH" "${QP_ROOT}"/include)'
         '',
         'source ${QP_ROOT}/install/EZFIO/Bash/ezfio.sh',
         '',