diff --git a/completions/git.completion.bash b/completions/git.completion.bash
index 751623b..4a7718b 100644
--- a/completions/git.completion.bash
+++ b/completions/git.completion.bash
@@ -1,3 +1,4 @@
+#! bash oh-my-bash.module
 # bash completion support for Git.
 _omb_completion_git_initialize() {
     if ! _omb_util_function_exists __gitdir; then
@@ -7,7 +8,7 @@ _omb_completion_git_initialize() {
         git_paths+=("/usr/bin/git")
         for path in "${git_paths[@]}"; do
             if [[ -L $path ]]; then
-                path=$(readlink -f $path)
+                path=$(_omb_util_readlink "$path")
             fi
             # Note: In the case of symbolic link, the true binary name can
             # contain prefix or suffix for architectures and versions.
diff --git a/lib/readlink.sh b/lib/readlink.sh
new file mode 100644
index 0000000..46f1f65
--- /dev/null
+++ b/lib/readlink.sh
@@ -0,0 +1,109 @@
+#! bash oh-my-bash.module
+
+## This module provides the following function which can be used as "readlink
+## -f" that can be used in any systems.  The implementation is taken from
+## "ble/util/readlink" from ble.sh <https://github.com/akinomyoga/ble.sh>.
+##
+## @fn _omb_util_readlink filename
+##   print the real path of the filename which is possibly a symbolic link.
+##
+
+_omb_module_require lib:utils
+
+if ((_omb_bash_version >= 40000)); then
+  _omb_util_readlink_visited_init='local -A visited=()'
+  function _omb_util_readlink__visited {
+    [[ ${visited[$1]+set} ]] && return 0
+    visited[$1]=1
+    return 1
+  }
+else
+  _omb_util_readlink_visited_init="local -a visited=()"
+  function _omb_util_readlink__visited {
+    local key
+    for key in "${visited[@]}"; do
+      [[ $1 == "$key" ]] && return 0
+    done
+    visited=("$1" "${visited[@]}")
+    return 1
+  }
+fi
+
+## @fn _omb_util_readlink__readlink path
+##   @var[out] link
+function _omb_util_readlink__readlink {
+  local path=$1
+  if _omb_util_function_exists readlink; then
+    link=$(readlink -- "$path")
+    [[ $link ]]
+  elif _omb_util_binary_exists ls; then
+    link=$(ls -ld -- "$path") &&
+      [[ $link == *" $path -> "?* ]] &&
+      link=${link#*" $path -> "}
+  else
+    false
+  fi
+} 2>/dev/null
+
+## @fn  _omb_util_readlink__resolve_physical_directory
+##   @var[in,out] path
+function _omb_util_readlink__resolve_physical_directory {
+  [[ $path == */?* ]] || return 0
+  local PWD=$PWD OLDPWD=$OLDPWD CDPATH=
+  builtin cd -L . &&
+    local pwd=$PWD &&
+    builtin cd -P "${path%/*}/" &&
+    path=${PWD%/}/${path##*/}
+  builtin cd -L "$pwd"
+  return 0
+}
+
+function _omb_util_readlink__resolve_loop {
+  local path=$1
+  builtin eval -- "$_omb_util_readlink_visited_init"
+  while [[ -h $path ]]; do
+    local link
+    _omb_util_readlink__visited "$path" && break
+    _omb_util_readlink__readlink "$path" || break
+    if [[ $link == /* || $path != */* ]]; then
+      path=$link
+    else
+      _omb_util_readlink__resolve_physical_directory
+      path=${path%/}/$link
+    fi
+    while [[ $path == ?*/ ]]; do path=${path%/}; done
+  done
+  echo "$path"
+}
+
+function _omb_util_readlink__resolve {
+  # Select implementation on the first call
+  _omb_util_readlink_type=
+
+  case $OSTYPE in
+  (cygwin | msys | linux-gnu)
+    # These systems provide "readlink -f".
+    local readlink
+    readlink=$(type -P readlink)
+    case $readlink in
+    (/bin/readlink | /usr/bin/readlink)
+      _omb_util_readlink_type=readlink-f
+      function _omb_util_readlink__resolve { readlink -f -- "$1"; } ;;
+    esac ;;
+  esac
+
+  if [[ ! $_omb_util_readlink_type ]]; then
+    _omb_util_readlink_type=loop
+    function _omb_util_readlink__resolve { _omb_util_readlink__resolve_loop "$1"; }
+  fi
+
+  _omb_util_readlink__resolve "$1"
+}
+
+function _omb_util_readlink {
+  if [[ -h $1 ]]; then
+    _omb_util_readlink__resolve "$1"
+  else
+    echo "$1"
+  fi
+}