diff --git a/lib_xua/src/core/endpoint0/descriptor_defs.h b/lib_xua/src/core/endpoint0/descriptor_defs.h
index 53ba28ed..1f29d58e 100644
--- a/lib_xua/src/core/endpoint0/descriptor_defs.h
+++ b/lib_xua/src/core/endpoint0/descriptor_defs.h
@@ -3,6 +3,11 @@
 #ifndef __DESCRIPTOR_DEFS_H__
 #define __DESCRIPTOR_DEFS_H__
 
+/*
+    Include xua.h to pick up the #defines of NUM_USB_CHAN_IN and NUM_USB_CHAN_OUT.
+ */
+#include "xua.h"
+
 #if (NUM_USB_CHAN_IN > 0) && (NUM_USB_CHAN_OUT > 0)
 #define AUDIO_INTERFACE_COUNT 3
 #elif (NUM_USB_CHAN_IN > 0) || (NUM_USB_CHAN_OUT > 0)