diff --git a/crates/py2erg/error.rs b/crates/py2erg/error.rs
index 20f1437..6c6bb9a 100644
--- a/crates/py2erg/error.rs
+++ b/crates/py2erg/error.rs
@@ -5,7 +5,6 @@ use erg_compiler::error::CompileError;
 
 pub(crate) fn reassign_func_error(
     input: Input,
-    errno: usize,
     loc: Location,
     caused_by: String,
     name: &str,
@@ -19,7 +18,7 @@ pub(crate) fn reassign_func_error(
                 "traditional_chinese" => format!("{name}已宣告，已被引用。不建議再次賦值"),
                 "english" => format!("{name} has already been declared and referenced. It is not recommended to reassign such a function"),
             ),
-            errno,
+            1,
             ErrorKind::AssignError,
             loc,
         ),
diff --git a/docs/source/errors.md b/docs/source/errors.md
new file mode 100644
index 0000000..c1cbc31
--- /dev/null
+++ b/docs/source/errors.md
@@ -0,0 +1,12 @@
+# Pylyzer-specific errors
+
+## E0001: Reassignment of a function referenced by other functions
+
+```python
+def g(): return f()
+
+def f(): return 1
+def f(): return "a" # E0001: Reassignment of a function referenced by other functions
+
+print(g())
+```