diff --git a/include/nuttx/audio/audio.h b/include/nuttx/audio/audio.h
index 8ce2b0cb1d..30d308eb57 100644
--- a/include/nuttx/audio/audio.h
+++ b/include/nuttx/audio/audio.h
@@ -462,6 +462,7 @@ struct ap_buffer_s
   apb_samp_t            nmaxbytes;  /* The maximum number of bytes */
   apb_samp_t            nbytes;     /* The number of bytes used */
   apb_samp_t            curbyte;    /* Next byte to be processed */
+  apb_samp_t            nsamples;   /* The number of samples in the buffer */
   mutex_t               lock;       /* Reference locking mutex */
   uint16_t              flags;      /* Buffer flags */
   uint16_t              crefs;      /* Number of reference counts */