diff --git a/Makefile b/Makefile
index 086000a13..e4d9ed52b 100644
--- a/Makefile
+++ b/Makefile
@@ -42,7 +42,7 @@ endif
 #
 
 # keep standard at C11 and C++11
-CFLAGS   = -I.              -I./include -I./include/CL -I./otherarch -I./otherarch/tools -O3 -DNDEBUG -std=c11   -fPIC
+CFLAGS   = -I.              -I./include -I./include/CL -I./otherarch -I./otherarch/tools -Ofast -DNDEBUG -std=c11   -fPIC
 CXXFLAGS = -I. -I./examples -I./include -I./include/CL -I./otherarch -I./otherarch/tools -O3 -DNDEBUG -std=c++11 -fPIC
 LDFLAGS  =