diff --git a/README.md b/README.md
index bc8429f4..7130279f 100644
--- a/README.md
+++ b/README.md
@@ -115,6 +115,10 @@ make
 * [nodelay](documentation/configuration.md#nodelay-yesno)
 * [keepalive](documentation/configuration.md#keepalive-integer)
 
+##### System
+
+* [coroutine\_stack\_size](documentation/configuration.md#coroutine_stack_size-integer)
+
 ##### Global limits
 
 * [client\_max](documentation/configuration.md#client_max-integer)
diff --git a/documentation/configuration.md b/documentation/configuration.md
index 10de3538..a08e4643 100644
--- a/documentation/configuration.md
+++ b/documentation/configuration.md
@@ -210,6 +210,17 @@ TCP keepalive time. Set to zero, to disable keepalive.
 
 `keepalive 7200`
 
+#### coroutine\_stack\_size *integer*
+
+Coroutine stack size.
+
+Set coroutine stack size in pages. In some rare cases
+it might be necessary to make stack size bigger. Actual stack will be
+allocated as `(coroutine_stack_size + 1_guard_page) * page_size`.
+Guard page is used to track stack overflows. Stack by default is set to 16KB.
+
+`coroutine_stack_size 4`
+
 #### client\_max *integer*
 
 Global limit of client connections.