diff --git a/src/modems/hayes/quirks.c b/src/modems/hayes/quirks.c
index 3fd7a15..8f023fb 100644
--- a/src/modems/hayes/quirks.c
+++ b/src/modems/hayes/quirks.c
@@ -16,6 +16,9 @@
 
 
 #include <sys/types.h>
+#ifdef DEBUG
+# include <stdio.h>
+#endif
 #include <string.h>
 #include "quirks.h"