diff --git a/docs/quick-start/config.md b/docs/quick-start/config.md
new file mode 100644
index 00000000..f302af4b
--- /dev/null
+++ b/docs/quick-start/config.md
@@ -0,0 +1,11 @@
+---
+icon: dot
+label: 'Advanced config'
+order: -2
+---
+
+You can create a `user_config.h` in the same directory as `pocketpy.h` to override some default settings.
+
+1. Copy [src/config.h](https://github.com/blueloveTH/pocketpy/blob/main/src/config.h) and rename it to `user_config.h`.
+2. Define a macro `PK_USER_CONFIG_H` in `user_config.h`. This invalidates the default `config.h` and enables your `user_config.h`.
+3. Edit `user_config.h` to override default settings.
\ No newline at end of file
diff --git a/src/config.h b/src/config.h
index 3e61abfc..29f1ca37 100644
--- a/src/config.h
+++ b/src/config.h
@@ -1,6 +1,6 @@
 #pragma once
 
-#ifdef PK_USER_CONFIG
+#ifdef PK_USER_CONFIG_H
 
 #include "user_config.h"
 
@@ -25,7 +25,7 @@
 
 // This is the maximum number of arguments in a function declaration
 // including positional arguments, keyword-only arguments, and varargs
-#define PK_MAX_CO_VARNAMES			255
+#define PK_MAX_CO_VARNAMES          255
 
 // Hash table load factor (smaller ones mean less collision but more memory)
 inline const float kInstAttrLoadFactor = 0.67f;