diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 978cb71e5d..11827e99d1 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -185,6 +185,7 @@ pre_initialize_variables () {
     export CTEST_OUTPUT_ON_FAILURE=1
 
     # CFLAGS and LDFLAGS for Asan builds that don't use CMake
+    # default to -O2, use -Ox _after_ this if you want another level
     ASAN_CFLAGS='-O2 -Werror -fsanitize=address,undefined -fno-sanitize-recover=all'
 
     # Gather the list of available components. These are the functions