diff --git a/GNUmakefile b/GNUmakefile
index bf979b6..08a7e00 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -27,7 +27,7 @@ path = $(subst :, ,$(PATH))
 diet_path = $(foreach dir,$(path),$(wildcard $(dir)/diet))
 ifeq ($(strip $(diet_path)),)
 ifneq ($(wildcard /opt/diet/bin/diet),)
-DIET=/opt/diet/bin/diet
+DIET=/opt/diet/bin/diet -Os
 else
 DIET=
 endif