diff --git a/libraries/AP_RCProtocol/AP_RCProtocol_FPort.cpp b/libraries/AP_RCProtocol/AP_RCProtocol_FPort.cpp
index 08bc5a06fa791..c16e2c2b4592a 100644
--- a/libraries/AP_RCProtocol/AP_RCProtocol_FPort.cpp
+++ b/libraries/AP_RCProtocol/AP_RCProtocol_FPort.cpp
@@ -179,7 +179,7 @@ void AP_RCProtocol_FPort::decode_downlink(const FPort_Frame &frame)
     buf[3] = telem_data.packet.appid & 0xFF;
     buf[4] = telem_data.packet.appid >> 8;
     memcpy(&buf[5], &telem_data.packet.data, 4);
-    buf[9] = crc_sum8(&buf[0], 9);
+    buf[9] = crc_sum8_with_carry(&buf[0], 9);
 
     // perform byte stuffing per FPort spec
     uint8_t len = 0;
@@ -307,7 +307,7 @@ void AP_RCProtocol_FPort::_process_byte(uint32_t timestamp_us, uint8_t b)
 bool AP_RCProtocol_FPort::check_checksum(void)
 {
     const uint8_t len = byte_input.buf[1]+2;
-    return crc_sum8(&byte_input.buf[1], len) == 0x00;
+    return crc_sum8_with_carry(&byte_input.buf[1], len) == 0x00;
 }
 
 // support byte input
diff --git a/libraries/AP_RCProtocol/AP_RCProtocol_FPort2.cpp b/libraries/AP_RCProtocol/AP_RCProtocol_FPort2.cpp
index dc9eceb61f8dd..2631f51d03025 100644
--- a/libraries/AP_RCProtocol/AP_RCProtocol_FPort2.cpp
+++ b/libraries/AP_RCProtocol/AP_RCProtocol_FPort2.cpp
@@ -179,7 +179,7 @@ void AP_RCProtocol_FPort2::decode_downlink(const FPort2_Frame &frame)
         // get fresh telem_data in the next call
         telem_data.available = false;
     }
-    buf[9] = crc_sum8(&buf[1], 8);
+    buf[9] = crc_sum8_with_carry(&buf[1], 8);
     
     uart->write(buf, sizeof(buf));
 #endif
@@ -286,7 +286,7 @@ void AP_RCProtocol_FPort2::_process_byte(uint32_t timestamp_us, uint8_t b)
 // check checksum byte
 bool AP_RCProtocol_FPort2::check_checksum(void)
 {
-    return crc_sum8(&byte_input.buf[1], byte_input.control_len-1) == 0;
+    return crc_sum8_with_carry(&byte_input.buf[1], byte_input.control_len-1) == 0;
 }
 
 // support byte input