diff --git a/libexec/rbenv-which b/libexec/rbenv-which
index 5d73673c..f656537d 100755
--- a/libexec/rbenv-which
+++ b/libexec/rbenv-which
@@ -15,40 +15,17 @@ if [ "$1" = "--complete" ]; then
   exec rbenv shims --short
 fi
 
-expand_path() {
-  if [ ! -d "$1" ]; then
-    return 1
-  fi
-
-  local cwd="$(pwd)"
-  cd "$1"
-  pwd
-  cd "$cwd"
-}
-
 remove_from_path() {
-  local path_to_remove="$(expand_path "$1")"
-  local result=""
-
-  if [ -z "$path_to_remove" ]; then
-    echo "${PATH}"
-    return
-  fi
-
-  local paths
-  IFS=: paths=($PATH)
-
-  for path in "${paths[@]}"; do
-    path="$(expand_path "$path" || true)"
-    if [ -n "$path" ] && [ "$path" != "$path_to_remove" ]; then
-      result="${result}${path}:"
-    fi
+  local path_to_remove="$1"
+  local path_before
+  local result=":$PATH:"
+  while [ "$path_before" != "$result" ]; do
+    path_before="$result"
+    result="${result//:$path_to_remove:/:}"
   done
-
   echo "${result%:}"
 }
 
-RBENV_VERSION="$(rbenv-version-name)"
 RBENV_COMMAND="$1"
 
 if [ -z "$RBENV_COMMAND" ]; then
@@ -56,6 +33,8 @@ if [ -z "$RBENV_COMMAND" ]; then
   exit 1
 fi
 
+RBENV_VERSION="${RBENV_VERSION:-$(rbenv-version-name)}"
+
 if [ "$RBENV_VERSION" = "system" ]; then
   PATH="$(remove_from_path "${RBENV_ROOT}/shims")"
   RBENV_COMMAND_PATH="$(command -v "$RBENV_COMMAND" || true)"
@@ -72,6 +51,9 @@ done
 
 if [ -x "$RBENV_COMMAND_PATH" ]; then
   echo "$RBENV_COMMAND_PATH"
+elif ! [ -d "${RBENV_ROOT}/versions/${RBENV_VERSION}" ]; then
+  echo "rbenv: version \`$RBENV_VERSION' is not installed" >&2
+  exit 1
 else
   echo "rbenv: $RBENV_COMMAND: command not found" >&2
 
diff --git a/test/which.bats b/test/which.bats
index a9d9f82a..6e68a0e6 100644
--- a/test/which.bats
+++ b/test/which.bats
@@ -31,6 +31,31 @@ create_executable() {
   assert_success "${RBENV_TEST_DIR}/bin/kill-all-humans"
 }
 
+@test "searches PATH for system version (shims prepended)" {
+  create_executable "${RBENV_TEST_DIR}/bin" "kill-all-humans"
+  create_executable "${RBENV_ROOT}/shims" "kill-all-humans"
+
+  PATH="${RBENV_ROOT}/shims:$PATH" RBENV_VERSION=system run rbenv-which kill-all-humans
+  assert_success "${RBENV_TEST_DIR}/bin/kill-all-humans"
+}
+
+@test "searches PATH for system version (shims appended)" {
+  create_executable "${RBENV_TEST_DIR}/bin" "kill-all-humans"
+  create_executable "${RBENV_ROOT}/shims" "kill-all-humans"
+
+  PATH="$PATH:${RBENV_ROOT}/shims" RBENV_VERSION=system run rbenv-which kill-all-humans
+  assert_success "${RBENV_TEST_DIR}/bin/kill-all-humans"
+}
+
+@test "searches PATH for system version (shims spread)" {
+  create_executable "${RBENV_TEST_DIR}/bin" "kill-all-humans"
+  create_executable "${RBENV_ROOT}/shims" "kill-all-humans"
+
+  PATH="${RBENV_ROOT}/shims:${RBENV_ROOT}/shims:/tmp/non-existent:$PATH:${RBENV_ROOT}/shims" \
+    RBENV_VERSION=system run rbenv-which kill-all-humans
+  assert_success "${RBENV_TEST_DIR}/bin/kill-all-humans"
+}
+
 @test "version not installed" {
   create_executable "2.0" "rspec"
   RBENV_VERSION=1.9 run rbenv-which rspec
@@ -72,3 +97,12 @@ SH
   assert_success
   assert_output "HELLO=:hello:ugly:world:again"
 }
+
+@test "discovers version from rbenv-version-name" {
+  mkdir -p "$RBENV_ROOT"
+  cat > "${RBENV_ROOT}/version" <<<"1.8"
+  create_executable "1.8" "ruby"
+
+  RBENV_VERSION= run rbenv-which ruby
+  assert_success "${RBENV_ROOT}/versions/1.8/bin/ruby"
+}