diff --git a/bacnet-stack/ports/bdk-atxx4-mstp/device.c b/bacnet-stack/ports/bdk-atxx4-mstp/device.c
index 755224fd..034046ea 100644
--- a/bacnet-stack/ports/bdk-atxx4-mstp/device.c
+++ b/bacnet-stack/ports/bdk-atxx4-mstp/device.c
@@ -778,7 +778,7 @@ int Device_Read_Property_Local(
         (rpdata->array_index != BACNET_ARRAY_ALL)) {
         rpdata->error_class = ERROR_CLASS_PROPERTY;
         rpdata->error_code = ERROR_CODE_PROPERTY_IS_NOT_AN_ARRAY;
-        apdu_len = -1;
+        apdu_len = BACNET_STATUS_ERROR;
     }
 
     return apdu_len;