diff --git a/docs/using-sdbus-c++.md b/docs/using-sdbus-c++.md
index 11dc4da..7cc2708 100644
--- a/docs/using-sdbus-c++.md
+++ b/docs/using-sdbus-c++.md
@@ -217,6 +217,8 @@ Let's have an object `/org/sdbuscpp/concatenator` that implements the `org.sdbus
 
 In the following sections, we will elaborate on the ways of implementing such an object on both the server and the client side.
 
+**Note:** In order to be able to call methods of your system bus-based D-Bus service, a D-Bus security policy file has to be put in place for that service. See [dbus-daemon documentation](https://dbus.freedesktop.org/doc/dbus-daemon.1.html), sections *INTEGRATING SYSTEM SERVICES* and *CONFIGURATION FILE*. As an example, you may look at the [policy file for sdbus-c++ integration tests](/tests/integrationtests/files/org.sdbuscpp.integrationtests.conf).
+
 Implementing the Concatenator example using basic sdbus-c++ API layer
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