diff --git a/README.md b/README.md
index c976a3c..3029888 100644
--- a/README.md
+++ b/README.md
@@ -45,14 +45,6 @@ source /the/directory/of/this/plugin/*.plugin.zsh
 
 **NOTE**: Don't source `*.zsh`! They will be sourced by `*.plugin.zsh` automatically.
 
-## Customize
-
-You can use your customized fzf-tab sources to override the default, such as:
-
-```zsh
-zstyle ':fzf-tab:sources' config-directory /the/directory/containing/your/source.zsh
-```
-
 ## Preview
 
 You need some optional tools:
@@ -223,6 +215,30 @@ display text.
 
 ![adb](https://user-images.githubusercontent.com/32936898/203727602-e33b617d-a218-435e-8f8a-585e7679857f.jpg)
 
+## Customize
+
+### Sources
+
+```zsh
+zstyle ':fzf-tab:sources' config-directory /a/directory
+```
+
+You can use your customized fzf-tab sources to override
+[this plugin's sources](sources).
+`*.zsh` in `config-directory` are standalone zsh scripts which can be syntax
+highlighted by your editor:
+
+```zsh
+# :fzf-tab:complete:context --optional-fzf-option
+foobar $word
+```
+
+- Built-in commands and aliases should start with `(\\|)` to support `\command`
+- Commands should start with `(\\|*/|)` to support `=command`
+
+That is, `\command <TAB>`, `=command <TAB>` will get same preview windows as
+`command <TAB>`.
+
 ### Similar Project
 
 - [fifc](https://github.com/gazorby/fifc):
diff --git a/fzf-tab-source.plugin.zsh b/fzf-tab-source.plugin.zsh
index f5dca1a..6a2887c 100644
--- a/fzf-tab-source.plugin.zsh
+++ b/fzf-tab-source.plugin.zsh
@@ -2,23 +2,22 @@
 0="${${ZERO:-${0:#$ZSH_ARGZERO}}:-${(%):-%N}}"
 0="${${(M)0:#/*}:-$PWD/$0}"
 
-# config
+local dir=${0:h} config_directory
 zstyle -s ':fzf-tab:sources' config-directory config_directory
-local sources=()
+local sources=($dir/sources/*.zsh)
+# use user's sources to override this plugin's sources
 if [[ -n $config_directory ]]; then
-  sources=($config_directory/**/*.zsh(.N))
+  sources+=($config_directory/**/*.zsh(.N))
 fi
 
 # https://github.com/Freed-Wu/fzf-tab-source/issues/11
 # enable $group
 zstyle ':completion:*:descriptions' format %d
 
-# use a standalone script to get syntax highlight
-# built-in commands and aliases should start with `(\\|)` to support `\command`
-# commands should start with `(\\|*/|)` to support `=command`
-local dir=${0:h} src line arr ctx flags
-for src in $dir/sources/*.zsh $sources; do
+local src line arr ctx flags
+for src in $sources; do
   while read -r line; do
+    # strip code to get magic comment
     arr=(${(@s. .)line##\# })
     ctx=${arr[1]}
     if [[ $ctx == ':fzf-tab:'* ]]; then