diff --git a/hello.c b/hello.c
index 9c5c7d1..a9d061d 100644
--- a/hello.c
+++ b/hello.c
@@ -1,5 +1,6 @@
 #include "stdio.h"
 #include "math.h"
+#include "complex.h"
 
 int main()
 {