diff --git a/firmware/Makefile b/firmware/Makefile
index 340359a9..387e543f 100644
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -125,7 +125,7 @@ DEBUG_PHONE_SNIFF?=0
 #CFLAGS+=-DUSB_NO_DEBUG=1
 
 # Optimization level, put in comment for debugging
-OPTIMIZATION ?= -O0
+OPTIMIZATION ?= -Os