diff --git a/os/imagezip/GNUmakefile.in b/os/imagezip/GNUmakefile.in
index 628cb8c1df5e2f7cbc6e1574ad3cd258ecdde8f0..09051a2723f84212e668a56725a2764704ba0da1 100644
--- a/os/imagezip/GNUmakefile.in
+++ b/os/imagezip/GNUmakefile.in
@@ -9,7 +9,7 @@ all:	imagezip imageunzip frisbee.o
 
 include $(TESTBED_SRCDIR)/GNUmakerules
 
-CFLAGS = -O -g -static
+CFLAGS = -O2 -g -static
 LIBS   = -lz
 
 imagezip: imagezip.o