diff --git a/doc/main.txt b/doc/main.txt
index 31648410f..1d6284cc2 100644
--- a/doc/main.txt
+++ b/doc/main.txt
@@ -14,7 +14,7 @@
  * The "core" module contains:
  *    - a Functor class: ns3::Callback
  *    - an os-independent interface to get write-only access to a file: ns3::SystemFile
- *    - an os-independent interface to get access to the elapsed wall clock time: ns3:SystemWallClockMs
+ *    - an os-independent interface to get access to the elapsed wall clock time: ns3::SystemWallClockMs
  *    - a class to register regression tests with the test manager: ns3::Test and ns3::TestManager
  *
  * The "simulator" module contains: