diff --git a/doc/en/scripting/builtins/libnetwork.md b/doc/en/scripting/builtins/libnetwork.md
index 515488f7..cef8facb 100644
--- a/doc/en/scripting/builtins/libnetwork.md
+++ b/doc/en/scripting/builtins/libnetwork.md
@@ -137,5 +137,5 @@ network.get_total_download() --> int
 
 ```lua
 -- Looks for a free port to use.
-network.find_free_port() --> int
+network.find_free_port() --> int or nil
 ```
diff --git a/doc/ru/scripting/builtins/libnetwork.md b/doc/ru/scripting/builtins/libnetwork.md
index 269b1615..5c107923 100644
--- a/doc/ru/scripting/builtins/libnetwork.md
+++ b/doc/ru/scripting/builtins/libnetwork.md
@@ -202,5 +202,5 @@ network.get_total_download() --> int
 
 ```lua
 -- Ищет свободный для использования порт.
-network.find_free_port() --> int
+network.find_free_port() --> int или nil
 ```