diff --git a/readme.txt b/readme.txt
index 7e02cd4..58a9498 100644
--- a/readme.txt
+++ b/readme.txt
@@ -45,7 +45,7 @@ be attached to it. Use "c" or "continue" in GDB to start execution.
 
 While debugging, it is useful to disable optimizations and enable debugging
 information. In "make-build.sh", under COMMON_CC_EXTRA_FLAGS, you can change
-"-O3" to "-Og -ggdb". Then, run these commands to rebuild:
+"-O3" to "-O0 -ggdb". Then, run these commands to rebuild:
   rm -r build
   rm build.ninja
   sh make-build.sh