diff --git a/src/modems/hayes/channel.c b/src/modems/hayes/channel.c
index 518260c..55d183d 100644
--- a/src/modems/hayes/channel.c
+++ b/src/modems/hayes/channel.c
@@ -16,6 +16,9 @@
 
 
 #include <stdlib.h>
+#ifdef DEBUG
+# include <stdio.h>
+#endif
 #include "command.h"
 #include "channel.h"