diff --git a/doc/sphinx/arm/install.rst b/doc/sphinx/arm/install.rst
index 7a198e6040..6a7a332f68 100644
--- a/doc/sphinx/arm/install.rst
+++ b/doc/sphinx/arm/install.rst
@@ -157,8 +157,8 @@ Building from source code requires the following software installed on
 the system:
 
 -  Boost C++ libraries (https://www.boost.org/). The oldest Boost version
-   used for testing is 1.57 (although Kea may also work with older
-   versions). The Boost system library must also be installed.
+   used for testing is 1.67 (although Kea may also work with older
+   versions e.g. 1.66). The Boost system library must also be installed.
    Installing a header-only version of Boost is not recommended.
 
 -  OpenSSL (at least version 1.0.2) or Botan (at least version 2).