diff --git a/doc/develop/west/build-flash-debug.rst b/doc/develop/west/build-flash-debug.rst
index 8fd6827217878a..44aa0bb500d8d0 100644
--- a/doc/develop/west/build-flash-debug.rst
+++ b/doc/develop/west/build-flash-debug.rst
@@ -208,11 +208,16 @@ build``, pass them after a ``--`` at the end of the command line.
 .. important::
 
    Passing additional CMake arguments like this forces ``west build`` to re-run
-   CMake, even if a build system has already been generated.
+   the CMake build configuration step, even if a build system has already been
+   generated.  This will make incremental builds slower (but still much faster
+   than building from scratch).
 
    After using ``--`` once to generate the build directory, use ``west build -d
    <build-dir>`` on subsequent runs to do incremental builds.
 
+   Alternatively, make your CMake arguments permanent as described in the next
+   section; it will not slow down incremental builds.
+
 For example, to use the Unix Makefiles CMake generator instead of Ninja (which
 ``west build`` uses by default), run::