diff --git a/bin/pyenv-virtualenv b/bin/pyenv-virtualenv
index 7fa241d..7070d73 100755
--- a/bin/pyenv-virtualenv
+++ b/bin/pyenv-virtualenv
@@ -8,6 +8,7 @@
 #
 
 PYENV_VIRTUALENV_VERSION="20130507"
+VIRTUALENV_VERSION="${VIRTUALENV_VERSION:-1.9.1}"
 
 set -e
 [ -n "$PYENV_DEBUG" ] && set -x
@@ -63,9 +64,40 @@ abs_dirname() {
   cd "$cwd"
 }
 
+http() {
+  local method="$1"
+  local url="$2"
+  local file="$3"
+  [ -n "$url" ] || return 1
+
+  if type curl &>/dev/null; then
+    "http_${method}_curl" "$url" "$file"
+  elif type wget &>/dev/null; then
+    "http_${method}_wget" "$url" "$file"
+  else
+    echo "error: please install \`curl\` or \`wget\` and try again" >&2
+    exit 1
+  fi
+}
+
+http_head_curl() {
+  curl -qsILf "$1" >&4 2>&1
+}
+
+http_get_curl() {
+  curl -C - -o "${2:--}" -qsSLf "$1"
+}
+
+http_head_wget() {
+  wget -q --spider "$1" >&4 2>&1
+}
+
+http_get_wget() {
+  wget -nv -c -O "${2:--}" "$1"
+}
+
 version() {
-  local VIRTUALENV_VERSION="$(pyenv-exec python "${VIRTUALENV}" --version || true)"
-  echo "pyenv-virtualenv ${PYENV_VIRTUALENV_VERSION} (virtualenv ${VIRTUALENV_VERSION:-unknown})"
+  echo "pyenv-virtualenv ${PYENV_VIRTUALENV_VERSION} (virtualenv ${VIRTUALENV_VERSION})"
 }
 
 usage() {
@@ -76,7 +108,13 @@ usage() {
 }
 
 PYENV_VIRTUALENV_ROOT="$(abs_dirname "$0")/.."
-VIRTUALENV="${PYENV_VIRTUALENV_ROOT}/libexec/pyenv-virtualenv/virtualenv.py"
+if [ -z "${PYENV_VIRTUALENV_CACHE_PATH}" ]; then
+  PYENV_VIRTUALENV_CACHE_PATH="${PYTHON_BUILD_CACHE_PATH:-${PYENV_ROOT}/cache}"
+fi
+if [ -z "${PYENV_VIRTUALENV_SCRIPT_PATH}" ]; then
+  PYENV_VIRTUALENV_SCRIPT_PATH="${PYENV_VIRTUALENV_ROOT}/libexec/pyenv-virtualenv"
+fi
+VIRTUALENV="${PYENV_VIRTUALENV_SCRIPT_PATH}/virtualenv.py"
 VIRTUALENV_OPTIONS=()
 
 parse_options "$@"
@@ -104,7 +142,7 @@ done
 
 PYTHON_BIN=$(PYENV_VERSION="${VERSION_NAME}" pyenv-which python)
 if [ ! -x "${PYTHON_BIN}" ]; then
-  echo "pyenv-virtualenv: could not obtain python executable: ${PYTHON_BIN}" >&2
+  echo "pyenv-virtualenv: could not find python executable: ${PYTHON_BIN}" >&2
   exit 1
 fi
 
@@ -130,9 +168,6 @@ VIRTUALENV_PATH="${PYENV_ROOT}/versions/${VIRTUALENV_NAME}"
 
 # virtualenv may download distribute/setuptools in current directory.
 # change to cache directory to reuse them between invocation.
-if [ -z "${PYENV_VIRTUALENV_CACHE_PATH}" ]; then
-  PYENV_VIRTUALENV_CACHE_PATH="${PYTHON_BUILD_CACHE_PATH:-${PYENV_ROOT}/cache}"
-fi
 mkdir -p "${PYENV_VIRTUALENV_CACHE_PATH}"
 {
   cd "${PYENV_VIRTUALENV_CACHE_PATH}"