diff --git a/man/sd_bus_call.xml b/man/sd_bus_call.xml
index fa0089bd22..1f7dfc2e82 100644
--- a/man/sd_bus_call.xml
+++ b/man/sd_bus_call.xml
@@ -89,6 +89,12 @@
input parameter; it can be used to propagate errors from the callback handler, it will not receive any
error that was received as method reply.)
+ The message m passed to the callback is only borrowed, that is, the callback should
+ not call sd_bus_message_unref3
+ on it. If the callback wants to hold on to the message beyond the lifetime of the callback, it needs to call
+ sd_bus_message_ref3 to create a
+ new reference.
+
If usec is zero, the default D-Bus method call timeout is used. See
sd_bus_get_method_call_timeout3.