diff --git a/README.adoc b/README.adoc
index 34eca4b..bc5db46 100644
--- a/README.adoc
+++ b/README.adoc
@@ -12768,7 +12768,11 @@ In order to use different build options, you might also want to use <<gem5-build
 
 ==== gem5 debug build
 
-Explained at: xref:debug-the-emulator[xrefstyle=full].
+How to use it in LKMC: xref:debug-the-emulator[xrefstyle=full].
+
+If you build gem5 with `scons build/ARM/gem5.debug`, then that is a `.debug` build.
+
+It relates to the more common `.opt` build just as explained at xref:debug-the-emulator[xrefstyle=full]: both `.opt` and `.debug` have `-g`, but `.opt` uses `-O2` while `.debug` uses `-O0`.
 
 ==== gem5 fast build