diff --git a/libexec/pyenv-which b/libexec/pyenv-which
index 8e2a6f4e..ccef0083 100755
--- a/libexec/pyenv-which
+++ b/libexec/pyenv-which
@@ -15,43 +15,17 @@ if [ "$1" = "--complete" ]; then
   exec pyenv 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%:}"
 }
 
-OLDIFS="$IFS"
-IFS=: versions=($(pyenv-version-name))
-IFS=: PYENV_VERSION="${versions[*]}"
-IFS="$OLDIFS"
 PYENV_COMMAND="$1"
 
 if [ -z "$PYENV_COMMAND" ]; then
@@ -59,6 +33,10 @@ if [ -z "$PYENV_COMMAND" ]; then
   exit 1
 fi
 
+OLDIFS="$IFS"
+IFS=: versions=(${PYENV_VERSION:-$(pyenv-version-name)})
+IFS="$OLDIFS"
+
 for version in "${versions[@]}"; do
   if [ "$version" = "system" ]; then
     PATH="$(remove_from_path "${PYENV_ROOT}/shims")"
@@ -67,6 +45,7 @@ for version in "${versions[@]}"; do
     PYENV_COMMAND_PATH="${PYENV_ROOT}/versions/${version}/bin/${PYENV_COMMAND}"
   fi
   if [ -x "$PYENV_COMMAND_PATH" ]; then
+    PYENV_VERSION="$version"
     break
   fi
 done
@@ -80,6 +59,9 @@ done
 
 if [ -x "$PYENV_COMMAND_PATH" ]; then
   echo "$PYENV_COMMAND_PATH"
+elif ! [ -d "${PYENV_ROOT}/versions/${PYENV_VERSION}" ]; then
+  echo "pyenv: version \`$PYENV_VERSION' is not installed" >&2
+  exit 1
 else
   echo "pyenv: $PYENV_COMMAND: command not found" >&2
 
diff --git a/test/which.bats b/test/which.bats
index dcce6665..d3b69f2b 100644
--- a/test/which.bats
+++ b/test/which.bats
@@ -21,6 +21,9 @@ create_executable() {
 
   PYENV_VERSION=3.4 run pyenv-which py.test
   assert_success "${PYENV_ROOT}/versions/3.4/bin/py.test"
+
+  PYENV_VERSION=3.4:2.7 run pyenv-which py.test
+  assert_success "${PYENV_ROOT}/versions/3.4/bin/py.test"
 }
 
 @test "searches PATH for system version" {
@@ -31,6 +34,31 @@ create_executable() {
   assert_success "${PYENV_TEST_DIR}/bin/kill-all-humans"
 }
 
+@test "searches PATH for system version (shims prepended)" {
+  create_executable "${PYENV_TEST_DIR}/bin" "kill-all-humans"
+  create_executable "${PYENV_ROOT}/shims" "kill-all-humans"
+
+  PATH="${PYENV_ROOT}/shims:$PATH" PYENV_VERSION=system run pyenv-which kill-all-humans
+  assert_success "${PYENV_TEST_DIR}/bin/kill-all-humans"
+}
+
+@test "searches PATH for system version (shims appended)" {
+  create_executable "${PYENV_TEST_DIR}/bin" "kill-all-humans"
+  create_executable "${PYENV_ROOT}/shims" "kill-all-humans"
+
+  PATH="$PATH:${PYENV_ROOT}/shims" PYENV_VERSION=system run pyenv-which kill-all-humans
+  assert_success "${PYENV_TEST_DIR}/bin/kill-all-humans"
+}
+
+@test "searches PATH for system version (shims spread)" {
+  create_executable "${PYENV_TEST_DIR}/bin" "kill-all-humans"
+  create_executable "${PYENV_ROOT}/shims" "kill-all-humans"
+
+  PATH="${PYENV_ROOT}/shims:${PYENV_ROOT}/shims:/tmp/non-existent:$PATH:${PYENV_ROOT}/shims" \
+    PYENV_VERSION=system run pyenv-which kill-all-humans
+  assert_success "${PYENV_TEST_DIR}/bin/kill-all-humans"
+}
+
 @test "version not installed" {
   create_executable "3.4" "py.test"
   PYENV_VERSION=3.3 run pyenv-which py.test
@@ -68,7 +96,19 @@ echo HELLO="\$(printf ":%s" "\${hellos[@]}")"
 exit
 SH
 
-  PYENV_HOOK_PATH="$hook_path" IFS=$' \t\n' run pyenv-which anything
+  PYENV_HOOK_PATH="$hook_path" IFS=$' \t\n' PYENV_VERSION=system run pyenv-which anything
   assert_success
   assert_output "HELLO=:hello:ugly:world:again"
 }
+
+@test "discovers version from pyenv-version-name" {
+  mkdir -p "$PYENV_ROOT"
+  cat > "${PYENV_ROOT}/version" <<<"3.4"
+  create_executable "3.4" "python"
+
+  mkdir -p "$PYENV_TEST_DIR"
+  cd "$PYENV_TEST_DIR"
+
+  PYENV_VERSION= run pyenv-which python
+  assert_success "${PYENV_ROOT}/versions/3.4/bin/python"
+}