diff --git a/bin/python-local-exec b/bin/python-local-exec
index a3068f67..62e59328 100755
--- a/bin/python-local-exec
+++ b/bin/python-local-exec
@@ -13,4 +13,11 @@
 
 set -e
 export PYENV_DIR="${1%/*}"
+
+[ -n "$PYENV_SILENCE_WARNINGS" ] || {
+  echo "pyenv: \`python-local-exec' is deprecated and will be removed in the next release."
+  echo "       To upgrade: https://github.com/yyuu/pyenv/wiki/python-local-exec"
+  echo
+} >&2
+
 exec python "$@"
diff --git a/completions/pyenv.bash b/completions/pyenv.bash
index cd6ddb1c..c8d8aa6c 100644
--- a/completions/pyenv.bash
+++ b/completions/pyenv.bash
@@ -5,8 +5,10 @@ _pyenv() {
   if [ "$COMP_CWORD" -eq 1 ]; then
     COMPREPLY=( $(compgen -W "$(pyenv commands)" -- "$word") )
   else
-    local command="${COMP_WORDS[1]}"
-    local completions="$(pyenv completions "$command")"
+    local words=("${COMP_WORDS[@]}")
+    unset words[0]
+    unset words[$COMP_CWORD]
+    local completions=$(pyenv completions "${words[@]}")
     COMPREPLY=( $(compgen -W "$completions" -- "$word") )
   fi
 }
diff --git a/completions/pyenv.zsh b/completions/pyenv.zsh
index f27cdbbc..75b977b9 100644
--- a/completions/pyenv.zsh
+++ b/completions/pyenv.zsh
@@ -5,14 +5,13 @@ fi
 compctl -K _pyenv pyenv
 
 _pyenv() {
-  local word words completions
+  local words completions
   read -cA words
-  word="${words[2]}"
 
   if [ "${#words}" -eq 2 ]; then
     completions="$(pyenv commands)"
   else
-    completions="$(pyenv completions "${word}")"
+    completions="$(pyenv completions "${words[2,-1]}")"
   fi
 
   reply=("${(ps:\n:)completions}")
diff --git a/libexec/pyenv-exec b/libexec/pyenv-exec
index 30f4191e..57fa0865 100755
--- a/libexec/pyenv-exec
+++ b/libexec/pyenv-exec
@@ -21,6 +21,7 @@ if [ "$1" = "--complete" ]; then
   exec pyenv shims --short
 fi
 
+export PYENV_VERSION="$(pyenv-version-name)"
 PYENV_COMMAND="$1"
 
 if [ -z "$PYENV_COMMAND" ]; then
@@ -36,5 +37,7 @@ for script in $(pyenv-hooks exec); do
 done
 
 shift 1
-export PATH="${PYENV_BIN_PATH}:${PATH}"
+if [ "$PYENV_VERSION" != "system" ]; then
+  export PATH="${PYENV_BIN_PATH}:${PATH}"
+fi
 exec -a "$PYENV_COMMAND" "$PYENV_COMMAND_PATH" "$@"
diff --git a/libexec/pyenv-init b/libexec/pyenv-init
index f8012827..fd2e2c2f 100755
--- a/libexec/pyenv-init
+++ b/libexec/pyenv-init
@@ -85,11 +85,12 @@ if [ -z "$no_rehash" ]; then
   echo 'pyenv rehash 2>/dev/null'
 fi
 
-commands=(`pyenv commands --sh`)
+commands=(`pyenv-commands --sh`)
 IFS="|"
 cat <<EOS
 pyenv() {
-  local command="\$1"
+  typeset command
+  command="\$1"
   if [ "\$#" -gt 0 ]; then
     shift
   fi
diff --git a/libexec/pyenv-rehash b/libexec/pyenv-rehash
index 13c327b3..447340ec 100755
--- a/libexec/pyenv-rehash
+++ b/libexec/pyenv-rehash
@@ -32,19 +32,48 @@ remove_prototype_shim() {
 
 # The prototype shim file is a script that re-execs itself, passing
 # its filename and any arguments to `pyenv exec`. This file is
-# hard-linked for every binary and then removed. The linking technique
-# is fast, uses less disk space than unique files, and also serves as
-# a locking mechanism.
+# hard-linked for every executable and then removed. The linking
+# technique is fast, uses less disk space than unique files, and also
+# serves as a locking mechanism.
 create_prototype_shim() {
   cat > "$PROTOTYPE_SHIM_PATH" <<SH
 #!/usr/bin/env bash
 set -e
+[ -n "\$PYENV_DEBUG" ] && set -x
+
+program="\${0##*/}"
+if [ "\$program" = "python" ]; then
+  for arg; do
+    case "\$arg" in
+    -c* | -- ) break ;;
+    */* )
+      if [ -f "\$arg" ]; then
+        export PYENV_DIR="\${arg%/*}"
+        break
+      fi
+      ;;
+    esac
+  done
+fi
+
 export PYENV_ROOT="$PYENV_ROOT"
-exec pyenv exec "\${0##*/}" "\$@"
+exec "$(command -v pyenv)" exec "\$program" "\$@"
 SH
   chmod +x "$PROTOTYPE_SHIM_PATH"
 }
 
+# If the contents of the prototype shim file differ from the contents
+# of the first shim in the shims directory, assume rbenv has been
+# upgraded and the existing shims need to be removed.
+remove_outdated_shims() {
+  for shim in *; do
+    if ! diff "$PROTOTYPE_SHIM_PATH" "$shim" >/dev/null 2>&1; then
+      for shim in *; do rm -f "$shim"; done
+    fi
+    break
+  done
+}
+
 # The basename of each argument passed to `make_shims` will be
 # registered for installation as a shim. In this way, plugins may call
 # `make_shims` with a glob to register many shims at once.
@@ -57,58 +86,27 @@ make_shims() {
   done
 }
 
-# Create an empty array for the list of registered shims.
+# Create an empty array for the list of registered shims and an empty
+# string to use as a search index.
 registered_shims=()
+registered_shims_index=""
 
 # We will keep track of shims registered for installation with the
-# global `reigstered_shims` array and with a global variable for each
-# shim. The array will let us iterate over all registered shims. The
-# global variables will let us quickly check whether a shim with the
-# given name has been registered or not.
+# global `reigstered_shims` array and with a global search index
+# string. The array will let us iterate over all registered shims. The
+# index string will let us quickly check whether a shim with the given
+# name has been registered or not.
 register_shim() {
   local shim="$@"
-  local var="$(shim_variable_name "$shim")"
-
-  if [ -z "${!var}" ]; then
-    registered_shims[${#registered_shims[*]}]="$shim"
-    eval "${var}=1"
-  fi
-}
-
-# To compute the global variable name for a given shim we must first
-# escape any non-alphanumeric characters. If the shim name is
-# alphanumeric (including a hyphen or underscore) we can take a
-# shorter path. Otherwise, we must iterate over each character and
-# escape the non-alphanumeric ones using `printf`.
-shim_variable_name() {
-  local shim="$1"
-  local result="_shim_"
-
-  if [[ ! "$shim" =~ [^[:alnum:]_-] ]]; then
-    shim="${shim//_/_5f}"
-    shim="${shim//-/_2d}"
-    result="$result$shim"
-  else
-    local length="${#shim}"
-    local char i
-
-    for ((i=0; i<length; i++)); do
-      char="${shim:$i:1}"
-      if [[ "$char" =~ [[:alnum:]] ]]; then
-        result="$result$char"
-      else
-        result="$result$(printf "_%02x" \'"$char")"
-      fi
-    done
-  fi
-
-  echo "$result"
+  registered_shims["${#registered_shims[@]}"]="$shim"
+  registered_shims_index="$registered_shims_index/$shim/"
 }
 
 # To install all the registered shims, we iterate over the
 # `registered_shims` array and create a link if one does not already
 # exist.
 install_registered_shims() {
+  local shim
   for shim in "${registered_shims[@]}"; do
     [ -e "$shim" ] || ln -f "$PROTOTYPE_SHIM_PATH" "$shim"
   done
@@ -119,11 +117,10 @@ install_registered_shims() {
 # in the directory but has not been registered as a shim should be
 # removed.
 remove_stale_shims() {
-  local var
+  local shim
   for shim in *; do
-    var="$(shim_variable_name "$shim")"
-    if [ -z "${!var}" ]; then
-      rm -f "$shim" 
+    if [[ "$registered_shims_index" != *"/$shim/"* ]]; then
+      rm -f "$shim"
     fi
   done
 }
@@ -131,10 +128,12 @@ remove_stale_shims() {
 
 # Change to the shims directory.
 cd "$SHIM_PATH"
-
-# Create the prototype shim, then register shims for all known binaries.
-create_prototype_shim
 shopt -s nullglob
+
+# Create the prototype shim, then register shims for all known
+# executables.
+create_prototype_shim
+remove_outdated_shims
 make_shims ../versions/*/bin/*
 
 # Restore the previous working directory.
diff --git a/libexec/pyenv-sh-rehash b/libexec/pyenv-sh-rehash
new file mode 100755
index 00000000..5d94d651
--- /dev/null
+++ b/libexec/pyenv-sh-rehash
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -e
+[ -n "$PYENV_DEBUG" ] && set -x
+
+# Provide pyenv completions
+if [ "$1" = "--complete" ]; then
+  exec pyenv-rehash --complete
+fi
+
+# When pyenv shell integration is enabled, delegate to pyenv-rehash,
+# then tell the shell to empty its command lookup cache.
+pyenv-rehash
+echo "hash -r"
diff --git a/libexec/pyenv-sh-shell b/libexec/pyenv-sh-shell
index e33c47e4..1121238a 100755
--- a/libexec/pyenv-sh-shell
+++ b/libexec/pyenv-sh-shell
@@ -37,11 +37,14 @@ fi
 
 if [ "$versions" = "--unset" ]; then
   echo "unset PYENV_VERSION"
-  exit 1
+  exit
 fi
 
 # Make sure the specified version is installed.
-pyenv-prefix "${versions[@]}" >/dev/null
-
-IFS=: PYENV_VERSION="${versions[*]}"
-echo "export PYENV_VERSION=\"${PYENV_VERSION}\""
+if pyenv-prefix "${versions[@]}" >/dev/null
+  IFS=: PYENV_VERSION="${versions[*]}"
+  echo "export PYENV_VERSION=\"${PYENV_VERSION}\""
+else
+  echo "return 1"
+  exit 1
+fi
diff --git a/libexec/pyenv-version-file-read b/libexec/pyenv-version-file-read
index c29577d8..cd752660 100755
--- a/libexec/pyenv-version-file-read
+++ b/libexec/pyenv-version-file-read
@@ -6,8 +6,8 @@ set -e
 VERSION_FILE="$1"
 
 if [ -e "$VERSION_FILE" ]; then
-  # Read and print the first non-whitespace word from the specified
-  # version file.
+  # Read the first non-whitespace word from the specified version file.
+  # Be careful not to load it whole in case there's something crazy in it.
   versions=()
   while read -a words; do
     word="${words[0]}"
diff --git a/libexec/pyenv-version-name b/libexec/pyenv-version-name
index 85d9c1d0..49a4aa34 100755
--- a/libexec/pyenv-version-name
+++ b/libexec/pyenv-version-name
@@ -17,10 +17,15 @@ if [ -z "$versions" ]; then
   exit
 fi
 
+version_exists() {
+  local version="$1"
+  [ -d "${RBENV_ROOT}/versions/${version}" ]
+}
+
 for version in "${versions[@]}"; do
   PYENV_VERSION_PATH="${PYENV_ROOT}/versions/${version}"
- 
-  if [ "$version" != "system" ] && [ ! -d "$PYENV_VERSION_PATH" ]; then
+
+  if [ "$version" != "system" ] && version_exists "$version"; then
     echo "pyenv: version \`$version' is not installed" >&2
     exit 1
   fi
diff --git a/libexec/pyenv-versions b/libexec/pyenv-versions
index 3dac25e3..648a7ed2 100755
--- a/libexec/pyenv-versions
+++ b/libexec/pyenv-versions
@@ -7,6 +7,20 @@
 set -e
 [ -n "$PYENV_DEBUG" ] && set -x
 
+if [ "$1" = "--bare" ]; then
+  hit_prefix=""
+  miss_prefix=""
+  IFS=: current_versions=()
+  version_origin=""
+  include_system=""
+else
+  hit_prefix="* "
+  miss_prefix="  "
+  IFS=: current_versions=($(pyenv-version-name || true))
+  version_origin=" (set by $(pyenv-version-origin))"
+  include_system="1"
+fi
+
 array_exists() {
   local x car="$1"
   shift
@@ -16,26 +30,21 @@ array_exists() {
   return 1
 }
 
-IFS=: PYENV_VERSION_NAMES=($(pyenv-version-name))
+print_version() {
+  if array_exists "$1" "${current_versions[@]}"; then
+    echo "${hit_prefix}${1}${version_origin}"
+  else
+    echo "${miss_prefix}${1}"
+  fi
+}
 
-if [ "$1" = "--bare" ]; then
-  hit_prefix=""
-  miss_prefix=""
-  version_origin=""
-else
-  hit_prefix="* "
-  miss_prefix="  "
-  version_origin=" (set by $(pyenv-version-origin))"
+# Include "system" in the non-bare output, if it exists
+if [ -n "$include_system" ] && PYENV_VERSION=system pyenv-which python >/dev/null 2>&1; then
+  print_version system
 fi
 
 for path in "${PYENV_ROOT}/versions/"*; do
   if [ -d "$path" ]; then
-    version="${path##*/}"
-
-    if array_exists "$version" "${PYENV_VERSION_NAMES[@]}"; then
-      echo "${hit_prefix}${version}${version_origin}"
-    else
-      echo "${miss_prefix}${version}"
-    fi
+    print_version "${path##*/}"
   fi
 done
diff --git a/libexec/pyenv-which b/libexec/pyenv-which
index afb8e3e9..283d894a 100755
--- a/libexec/pyenv-which
+++ b/libexec/pyenv-which
@@ -77,5 +77,15 @@ if [ -x "$PYENV_COMMAND_PATH" ]; then
   echo "$PYENV_COMMAND_PATH"
 else
   echo "pyenv: $PYENV_COMMAND: command not found" >&2
+
+  versions="$(pyenv-whence "$PYENV_COMMAND" || true)"
+  if [ -n "$versions" ]; then
+    { echo
+      echo "The \`$1' command exists in these Ruby versions:"
+      echo "$versions" | sed 's/^/  /g'
+      echo
+    } >&2
+  fi
+
   exit 127
 fi