diff --git a/bacnet-stack/src/abort.c b/bacnet-stack/src/abort.c
index 0b061c21..381bdb56 100644
--- a/bacnet-stack/src/abort.c
+++ b/bacnet-stack/src/abort.c
@@ -63,7 +63,8 @@ BACNET_ABORT_REASON abort_convert_error_code(
             abort_code = ABORT_REASON_SEGMENTATION_NOT_SUPPORTED;
             break;
         case ERROR_CODE_ABORT_PROPRIETARY:
-            abort_code = FIRST_PROPRIETARY_ABORT_REASON;
+            abort_code =
+                (BACNET_ABORT_REASON)FIRST_PROPRIETARY_ABORT_REASON;
             break;
         case ERROR_CODE_ABORT_OTHER:
         default:
diff --git a/bacnet-stack/src/reject.c b/bacnet-stack/src/reject.c
index 3bb63e9f..163e0bea 100644
--- a/bacnet-stack/src/reject.c
+++ b/bacnet-stack/src/reject.c
@@ -80,7 +80,8 @@ BACNET_REJECT_REASON reject_convert_error_code(
             reject_code = REJECT_REASON_UNRECOGNIZED_SERVICE;
             break;
         case ERROR_CODE_REJECT_PROPRIETARY:
-            reject_code = FIRST_PROPRIETARY_REJECT_REASON;
+            reject_code =
+                (BACNET_REJECT_REASON)FIRST_PROPRIETARY_REJECT_REASON;
             break;
         case ERROR_CODE_REJECT_OTHER:
         default: