diff --git a/libexec/rbenv-exec b/libexec/rbenv-exec
index f3908f8d..a9309d0e 100755
--- a/libexec/rbenv-exec
+++ b/libexec/rbenv-exec
@@ -2,59 +2,24 @@
 #
 # Summary: Run an executable with the selected Ruby version
 #
-# Usage: rbenv exec <command> [args...]
+# Usage: rbenv exec <command> [arg1 arg2...]
 #
-# Runs an executable contained by the currently selected Ruby's bin
-# directory. Rough equivalent of:
+# Runs an executable by first preparing PATH so that the selected Ruby
+# version's `bin' directory is at the front.
 #
-#   exec "$(rbenv prefix)/bin/$command" args...
+# For example, if the currently selected Ruby version is 1.9.3-p327:
+#   rbenv exec bundle install
+#
+# is equivalent to:
+#   PATH="$RBENV_ROOT/versions/1.9.3-p327/bin:$PATH" bundle install
 
 set -e
 [ -n "$RBENV_DEBUG" ] && set -x
 
-rubypath=""
 # Provide rbenv completions
-while true; do
-  case "$1" in
-  "--complete" )
-    exec rbenv shims --short
-    ;;
-  "--rubypath" )
-    rubypath=1
-    shift 1
-    ;;
-  * )
-    break
-    ;;
-  esac
-done
-
-# Replace any "RBENV_ROOT/shims" or "RBENV_ROOT/versions/*/bin" paths in the
-# list with the given path. If no replacements were made, prepend the path onto
-# the list.
-replace_shims_path() {
-  local path="$1"
-  local dir="$2"
-  # fake directory that serves as a placeholder for shims location in RUBYPATH:
-  local placeholder="/rbenv_shims_were_here"
-  local found=""
-  local result=""
-  local -a paths
-  IFS=: paths=($path)
-
-  for path in "${paths[@]}"; do
-    if [[ $path = "${RBENV_ROOT}/shims" || $path == "${RBENV_ROOT}/versions/"*/bin || $path = $placeholder ]]; then
-      found=1
-      result="${result}${dir:-$placeholder}:"
-    else
-      result="${result}${path}:"
-    fi
-  done
-
-  # if no rbenv paths were replaced, simply prepend the path
-  [ -n "$found" -o -z "$dir" ] || result="${dir}:${path}"
-  echo "${result%:}"
-}
+if [ "$1" = "--complete" ]; then
+  exec rbenv shims --short
+fi
 
 RBENV_VERSION="$(rbenv-version-name)"
 RBENV_COMMAND="$1"
@@ -66,6 +31,7 @@ fi
 
 export RBENV_VERSION
 RBENV_COMMAND_PATH="$(rbenv-which "$RBENV_COMMAND")"
+RBENV_BIN_PATH="${RBENV_COMMAND_PATH%/*}"
 
 OLDIFS="$IFS"
 IFS=$'\n' scripts=(`rbenv-hooks exec`)
@@ -75,9 +41,7 @@ for script in "${scripts[@]}"; do
 done
 
 shift 1
-if [ -n "$rubypath" ]; then
-  bindir=""
-  [ "$RBENV_VERSION" != "system" ] && bindir="${RBENV_COMMAND_PATH%/*}"
-  export RUBYPATH="$(replace_shims_path "${RUBYPATH:-$PATH}" "$bindir")"
+if [ "$RBENV_VERSION" != "system" ]; then
+  export PATH="${RBENV_BIN_PATH}:${PATH}"
 fi
 exec -a "$RBENV_COMMAND" "$RBENV_COMMAND_PATH" "$@"
diff --git a/libexec/rbenv-rehash b/libexec/rbenv-rehash
index 4bcc944d..5ec195ec 100755
--- a/libexec/rbenv-rehash
+++ b/libexec/rbenv-rehash
@@ -45,12 +45,10 @@ create_prototype_shim() {
 set -e
 [ -n "\$RBENV_DEBUG" ] && set -x
 
-opt=""
 program="\${0##*/}"
 if [ "\$program" = "ruby" ]; then
   for arg; do
     case "\$arg" in
-    -S* ) opt=--rubypath ;;
     -e* | -- ) break ;;
     */* )
       if [ -f "\$arg" ]; then
@@ -63,7 +61,7 @@ if [ "\$program" = "ruby" ]; then
 fi
 
 export RBENV_ROOT="$RBENV_ROOT"
-exec "$(command -v rbenv)" exec \$opt "\$program" "\$@"
+exec "$(command -v rbenv)" exec "\$program" "\$@"
 SH
   chmod +x "$PROTOTYPE_SHIM_PATH"
 }
diff --git a/test/exec.bats b/test/exec.bats
index f82a42ef..889eb897 100644
--- a/test/exec.bats
+++ b/test/exec.bats
@@ -3,37 +3,15 @@
 load test_helper
 
 create_executable() {
-  local file="${1?}"
-  [[ $file == */* ]] || file="${RBENV_ROOT}/versions/${RBENV_VERSION}/bin/$file"
+  name="${1?}"
   shift 1
-  mkdir -p "${file%/*}"
+  bin="${RBENV_ROOT}/versions/${RBENV_VERSION}/bin"
+  mkdir -p "$bin"
   { if [ $# -eq 0 ]; then cat -
     else echo "$@"
     fi
-  } | sed -Ee '1s/^[[:space:]]+//' > "$file"
-  chmod +x "$file"
-}
-
-# Fake ruby executable that emulates `ruby -S <cmd>' behavior by running the
-# first `cmd' found in RUBYPATH/PATH as bash script.
-create_ruby_executable() {
-  create_executable "${1:-ruby}" <<SH
-#!$BASH
-if [[ \$1 == "-S"* ]]; then
-  cmd="\${1#-S}"
-  [ -n "\$cmd" ] || cmd="\$2"
-  found="\$(PATH="\${RUBYPATH:-\$PATH}" \$(command -v which) \$cmd)"
-  # assert that the found executable has ruby for shebang
-  if head -1 "\$found" | grep ruby >/dev/null; then
-    \$BASH "\$found"
-  else
-    echo "ruby: no Ruby script found in input (LoadError)" >&2
-    exit 1
-  fi
-else
-  echo 'ruby (rbenv test)'
-fi
-SH
+  } | sed -Ee '1s/^ +//' > "${bin}/$name"
+  chmod +x "${bin}/$name"
 }
 
 @test "fails with invalid version" {
@@ -104,56 +82,26 @@ ${RBENV_ROOT}/versions/2.0/bin/ruby
 OUT
 }
 
-@test "doesn't mutate PATH" {
-  export RBENV_VERSION="2.0"
-  create_executable "ruby" <<SH
-#!$BASH
-echo \$PATH
-SH
-
-  run rbenv-exec ruby
-  assert_success "$PATH"
-}
-
-@test "doesn't set RUBYPATH" {
-  export RBENV_VERSION="2.0"
-  create_executable "ruby" <<SH
-#!$BASH
-echo \$RUBYPATH
-SH
-
-  RUBYPATH="" run rbenv-exec ruby
-  assert_success
-  assert_output ""
-}
-
-@test "allows subprocesses to select a different RBENV_VERSION" {
-  RBENV_VERSION=1.8 create_executable "rake" <<SH
-#!$BASH
-echo rake 1.8
-SH
-
-  export RBENV_VERSION="2.0"
-  create_executable "rake" "#!/bin/sh"
-  create_executable "ruby" <<SH
-#!$BASH
-echo ruby 2.0
-RBENV_VERSION=1.8 exec rake
-SH
-
-  rbenv rehash
-  run ruby
-  assert_success
-  assert_output <<OUT
-ruby 2.0
-rake 1.8
-OUT
-}
-
 @test "supports ruby -S <cmd>" {
   export RBENV_VERSION="2.0"
 
-  create_ruby_executable
+  # emulate `ruby -S' behavior
+  create_executable "ruby" <<SH
+#!$BASH
+if [[ \$1 == "-S"* ]]; then
+  found="\$(PATH="\${RUBYPATH:-\$PATH}" which \$2)"
+  # assert that the found executable has ruby for shebang
+  if head -1 "\$found" | grep ruby >/dev/null; then
+    \$BASH "\$found"
+  else
+    echo "ruby: no Ruby script found in input (LoadError)" >&2
+    exit 1
+  fi
+else
+  echo 'ruby 2.0 (rbenv test)'
+fi
+SH
+
   create_executable "rake" <<SH
 #!/usr/bin/env ruby
 echo hello rake
@@ -163,151 +111,3 @@ SH
   run ruby -S rake
   assert_success "hello rake"
 }
-
-@test "supports ruby -S with system version" {
-  export RBENV_VERSION=2.0
-  create_executable "ruby" "#!/bin/sh"
-  create_executable "rake" "#!/bin/sh"
-  rbenv-rehash
-
-  create_ruby_executable "${RBENV_TEST_DIR}/bin/ruby"
-  create_executable "${RBENV_TEST_DIR}/bin/rake" <<SH
-#!/usr/bin/env ruby
-echo system rake
-SH
-
-  RBENV_VERSION=system run ruby -S rake
-  assert_success "system rake"
-}
-
-@test "ruby -S allows commands higher in PATH to have precedence over shims" {
-  export RBENV_VERSION="2.0"
-
-  create_ruby_executable
-  create_executable "rake" <<SH
-#!/usr/bin/env ruby
-echo normal rake
-SH
-  rbenv-rehash
-
-  create_executable "${HOME}/bin/rake" <<SH
-#!/usr/bin/env ruby
-echo override rake
-SH
-
-  PATH="${HOME}/bin:$PATH" run ruby -S rake
-  assert_success "override rake"
-}
-
-@test "ruby -S respects existing RUBYPATH" {
-  export RBENV_VERSION="2.0"
-
-  create_ruby_executable
-  create_executable "rspec" <<SH
-#!/usr/bin/env ruby
-echo normal rspec
-SH
-  rbenv-rehash
-
-  create_executable "${HOME}/bin/rspec" "#!/bin/sh"
-  create_executable "${HOME}/bin/rake" <<SH
-#!/usr/bin/env ruby
-echo override rake
-SH
-
-  export RUBYPATH="${HOME}/bin"
-  run ruby -S rspec
-  assert_success "normal rspec"
-  run ruby -S rake
-  assert_success "override rake"
-}
-
-@test "supports nested ruby -S invocations to change RBENV_VERSION" {
-  export RBENV_VERSION="1.8"
-  create_ruby_executable
-  create_executable "rspec" <<SH
-#!/usr/bin/env ruby
-echo rspec 1.8
-SH
-
-  export RBENV_VERSION="2.0"
-  create_ruby_executable
-  create_executable "rspec" <<SH
-#!/usr/bin/env ruby
-echo rspec 2.0
-SH
-  create_executable "rake" <<SH
-#!/usr/bin/env ruby
-echo rake 2.0
-RBENV_VERSION=1.8 ruby -S rspec
-SH
-
-  rbenv-rehash
-  run ruby -S rake
-  assert_success
-  assert_output <<OUT
-rake 2.0
-rspec 1.8
-OUT
-}
-
-@test "supports system ruby -S invocation to select a different RBENV_VERSION" {
-  export RBENV_VERSION="2.0"
-  create_ruby_executable
-  create_executable "rspec" <<SH
-#!/usr/bin/env ruby
-echo rspec 2.0
-SH
-  rbenv-rehash
-
-  create_ruby_executable "${RBENV_TEST_DIR}/bin/ruby"
-  create_executable "${RBENV_TEST_DIR}/bin/rspec" <<SH
-#!/usr/bin/env ruby
-echo system rspec
-SH
-  create_executable "${RBENV_TEST_DIR}/bin/rake" <<SH
-#!/usr/bin/env ruby
-echo system rake
-RBENV_VERSION=2.0 ruby -S rspec
-SH
-
-  RBENV_VERSION=system run ruby -S rake
-  assert_success
-  assert_output <<OUT
-system rake
-rspec 2.0
-OUT
-}
-
-@test "nested ruby -S invocations preserve PATH precedence" {
-  export RBENV_VERSION="2.0"
-  create_ruby_executable
-  create_executable "rspec" <<SH
-#!/usr/bin/env ruby
-echo rspec 2.0
-SH
-  rbenv-rehash
-
-  create_ruby_executable "${RBENV_TEST_DIR}/bin/ruby"
-  create_executable "${RBENV_TEST_DIR}/bin/rspec" <<SH
-#!/usr/bin/env ruby
-echo system rspec
-SH
-  create_executable "${RBENV_TEST_DIR}/bin/rake" <<SH
-#!/usr/bin/env ruby
-echo system rake
-RBENV_VERSION=2.0 ruby -S rspec
-SH
-
-  create_executable "${HOME}/bin/rspec" <<SH
-#!/usr/bin/env ruby
-echo override rspec
-SH
-
-  PATH="${HOME}/bin:$PATH" RBENV_VERSION=system run ruby -S rake
-  assert_success
-  assert_output <<OUT
-system rake
-override rspec
-OUT
-}