diff --git a/README.md b/README.md
index 5eee13a..c13ef29 100644
--- a/README.md
+++ b/README.md
@@ -98,5 +98,5 @@ By default, this Makefile includes `-Werror`, which **treats all warnings as err
 
 You can tweak optimization levels and sanitizers at the top of the file:
 
-* **Debug (`DEBUG_FLAGS`):** Defaults to `-g3 -O0 -fsanitize=undefined -fno-omit-frame-pointer`. You can add Address Sanitizer by appending `-fsanitize=address`.
+* **Debug (`DEBUG_FLAGS`):** Defaults to `-g3 -O0 -fsanitize=undefined -fno-omit-frame-pointer`. You can add Address Sanitizer by replacing `undefined` with `address`. (after the `-fsanitize=` flag)
 * **Release (`RELEASE_FLAGS`):** Defaults to `-O2 -D NDEBUG`. (`NDEBUG` strips out `assert()` calls). If you want maximum optimization, you can change `-O2` to `-O3` or `-Ofast` (use `-Ofast` with caution as it breaks strict IEEE compliance for math).
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