diff --git a/lib/c/Makefile b/lib/c/Makefile
index 8b531d69..9cac1ff0 100644
--- a/lib/c/Makefile
+++ b/lib/c/Makefile
@@ -1,4 +1,4 @@
-CFLAGS = -o3 -Wall
+CFLAGS = -O3 -Wall
 
 parse_int.o: parse_int.c
-	gcc -c $< $(CFLAGS) -o $@
\ No newline at end of file
+	gcc -c $< $(CFLAGS) -o $@