diff --git a/include/dtmf.h b/include/dtmf.h
index 05d6a1afe..96ae42308 100644
--- a/include/dtmf.h
+++ b/include/dtmf.h
@@ -3,6 +3,7 @@
 
 #include <inttypes.h>
 #include <glib.h>
+#include <errno.h>
 #include "str.h"