diff --git a/ports/stm32f4xx/dlmstp.c b/ports/stm32f4xx/dlmstp.c
index c07b46f4..ae85b101 100644
--- a/ports/stm32f4xx/dlmstp.c
+++ b/ports/stm32f4xx/dlmstp.c
@@ -394,7 +394,7 @@ static uint16_t MSTP_Create_Frame(uint8_t *buffer,
         if (frame_type == FRAME_TYPE_BACNET_DATA_EXPECTING_REPLY) {
             frame_type = FRAME_TYPE_BACNET_EXTENDED_DATA_EXPECTING_REPLY;
             cobs_bacnet_frame = true;
-        } else if (frame_type == FRAME_TYPE_BACNET_DATA_EXPECTING_REPLY) {
+        } else if (frame_type == FRAME_TYPE_BACNET_DATA_NOT_EXPECTING_REPLY) {
             frame_type = FRAME_TYPE_BACNET_EXTENDED_DATA_NOT_EXPECTING_REPLY;
             cobs_bacnet_frame = true;
         } else if ((frame_type < Nmin_COBS_type) ||
diff --git a/src/bacnet/datalink/mstp.c b/src/bacnet/datalink/mstp.c
index c2c40dff..b8ea9c6f 100644
--- a/src/bacnet/datalink/mstp.c
+++ b/src/bacnet/datalink/mstp.c
@@ -261,7 +261,7 @@ uint16_t MSTP_Create_Frame(uint8_t *buffer,
         if (frame_type == FRAME_TYPE_BACNET_DATA_EXPECTING_REPLY) {
             frame_type = FRAME_TYPE_BACNET_EXTENDED_DATA_EXPECTING_REPLY;
             cobs_bacnet_frame = true;
-        } else if (frame_type == FRAME_TYPE_BACNET_DATA_EXPECTING_REPLY) {
+        } else if (frame_type == FRAME_TYPE_BACNET_DATA_NOT_EXPECTING_REPLY) {
             frame_type = FRAME_TYPE_BACNET_EXTENDED_DATA_NOT_EXPECTING_REPLY;
             cobs_bacnet_frame = true;
         } else if ((frame_type < Nmin_COBS_type) ||