diff --git a/source/preparing-software.adoc b/source/preparing-software.adoc
index 079931d..fbfa008 100644
--- a/source/preparing-software.adoc
+++ b/source/preparing-software.adoc
@@ -215,6 +215,10 @@ clean:
 
 ----
 
+WARNING: The ``-g`` flag is required with ``gcc`` because ``rpmbuild`` needs debug
+information by default. Alternatively, you can disable `debug_package` by adding
+`%global debug_package %{nil}` line to the `cello.spec`.
+
 Now to build the software, simply run ``make``:
 
 [source,bash]