Change to O3 since it's faster than O2 now
diff --git a/Makefile b/Makefile
index 019d1a8..5407de8 100644
--- a/Makefile
+++ b/Makefile
@@ -1,8 +1,8 @@
 CC ?= gcc
 CXX ?= g++
 
-override CFLAGS := -W -Wall -Wextra -ansi -pedantic -lm -O2 -Wno-unused-function -fPIC $(CFLAGS)
-override CXXFLAGS := -W -Wall -Wextra -ansi -pedantic -O2 -fPIC $(CXXFLAGS)
+override CFLAGS := -W -Wall -Wextra -ansi -pedantic -lm -O3 -Wno-unused-function -fPIC $(CFLAGS)
+override CXXFLAGS := -W -Wall -Wextra -ansi -pedantic -O3 -fPIC $(CXXFLAGS)
 
 ZOPFLILIB_SRC = src/zopfli/blocksplitter.c src/zopfli/cache.c\
                 src/zopfli/deflate.c src/zopfli/gzip_container.c\