diff --git a/src/output_internal.h b/src/output_internal.h
index dc363a6b9..e53fc6a61 100644
--- a/src/output_internal.h
+++ b/src/output_internal.h
@@ -20,6 +20,7 @@
 #ifndef MPD_OUTPUT_INTERNAL_H
 #define MPD_OUTPUT_INTERNAL_H
 
+#include "output_api.h"
 #include "pcm_convert.h"
 #include "notify.h"