diff --git a/docs/api/session.md b/docs/api/session.md
index 2a19f6576f38..ee509e1b8293 100644
--- a/docs/api/session.md
+++ b/docs/api/session.md
@@ -563,7 +563,7 @@ response are visible by the time this listener is fired.
   * `timestamp` Double
   * `requestHeaders` Object
 
-#### `webRequest.onHeadersReceived([filter,]listener)`
+#### `webRequest.onHeadersReceived([filter, ]listener)`
 
 * `filter` Object
 * `listener` Function