diff --git a/man2/epoll_wait.2 b/man2/epoll_wait.2
index 963790644..48bb28134 100644
--- a/man2/epoll_wait.2
+++ b/man2/epoll_wait.2
@@ -55,6 +55,9 @@ The
 argument specifies the number of milliseconds that
 .BR epoll_wait ()
 will block.
+Time is measured against the
+.B CLOCK_MONOTONIC
+clock.
 The call will block until either:
 .IP * 3
 a file descriptor delivers an event;