diff --git a/src/global.mk b/src/global.mk
index 6a372c9..b7e01e4 100644
--- a/src/global.mk
+++ b/src/global.mk
@@ -3,7 +3,7 @@ LIBPATH= -LlibecoPCR -Llibecoprimer -Llibthermo -L/usr/local/lib
 MAKEDEPEND = gcc -D$(MACHINE) -M $(CPPFLAGS) -o $*.d $<
 
 CC=gcc
-CFLAGS= -W -Wall -05
+CFLAGS= -W -Wall -O5
 #CFLAGS= -W -Wall -O5 -m64 -g
 #CFLAGS= -W -Wall -O0 -m64  -g
 #CFLAGS= -W -Wall -O5 -fast -g