diff --git a/include/rtl-sdr.h b/include/rtl-sdr.h
index 04b0fad..14689cc 100644
--- a/include/rtl-sdr.h
+++ b/include/rtl-sdr.h
@@ -86,8 +86,8 @@ RTLSDR_API int rtlsdr_wait_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, v
  * \param ctx user specific context to pass via the callback function
  * \param buf_num optional buffer count, buf_num * buf_len = overall buffer size
  *		  set to 0 for default buffer count (32)
- * \param buf_len optional buffer length, must be multiple of 2,
- *		  set to 0 for default buffer length (16 * 16384)
+ * \param buf_len optional buffer length, must be multiple of 512,
+ *		  set to 0 for default buffer length (16 * 32 * 512)
  * \return 0 on success
  */
 RTLSDR_API int rtlsdr_read_async(rtlsdr_dev_t *dev,
diff --git a/src/rtl-sdr.c b/src/rtl-sdr.c
index 6e40225..761ce49 100644
--- a/src/rtl-sdr.c
+++ b/src/rtl-sdr.c
@@ -141,7 +141,7 @@ static rtlsdr_device_t devices[] = {
 };
 
 #define DEFAULT_BUF_NUMBER	32
-#define DEFAULT_BUF_LENGTH	(16 * 16384)
+#define DEFAULT_BUF_LENGTH	(16 * 32 * 512)
 
 enum rtlsdr_async_status {
 	RTLSDR_INACTIVE = 0,
@@ -891,7 +891,7 @@ int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx,
 	else
 		dev->xfer_buf_num = DEFAULT_BUF_NUMBER;
 
-	if (buf_len > 0 && buf_len % 2 == 0) /* len must be multiple of 2 */
+	if (buf_len > 0 && buf_len % 512 == 0) /* len must be multiple of 512 */
 		dev->xfer_buf_len = buf_len;
 	else
 		dev->xfer_buf_len = DEFAULT_BUF_LENGTH;