diff --git a/flow.c b/flow.c
index d24726d..a8aeb15 100644
--- a/flow.c
+++ b/flow.c
@@ -6,6 +6,7 @@
  */
 
 #include <stdint.h>
+#include <stdio.h>
 #include <unistd.h>
 #include <string.h>