diff --git a/Makefile b/Makefile
index 4bc096e..cca4428 100644
--- a/Makefile
+++ b/Makefile
@@ -213,7 +213,7 @@ ifneq (,$(COVERAGE))
 C_FLAGS += --coverage -O1
 SAIL_FLAGS += -Oconstant_fold
 else
-C_OPT_FLAGS ?= -O2 -flto
+C_OPT_FLAGS ?= -O2 -flto=auto
 C_FLAGS += $(C_OPT_FLAGS)
 endif