diff --git a/libraries/AP_GPS/AP_GPS_ERB.cpp b/libraries/AP_GPS/AP_GPS_ERB.cpp
index 502b3fd7d98..90fca59c44a 100644
--- a/libraries/AP_GPS/AP_GPS_ERB.cpp
+++ b/libraries/AP_GPS/AP_GPS_ERB.cpp
@@ -79,7 +79,7 @@ AP_GPS_ERB::read(void)
             }
             _step = 0;
             Debug("reset %u", __LINE__);
-            /* no break */
+            FALLTHROUGH;
         case 0:
             if(PREAMBLE1 == data)
                 _step++;
@@ -238,7 +238,7 @@ reset:
                 break;
             }
             state.step = 0;
-            /* no break */
+            FALLTHROUGH;
         case 0:
             if (PREAMBLE1 == data)
                 state.step++;
diff --git a/libraries/AP_GPS/AP_GPS_MTK.cpp b/libraries/AP_GPS/AP_GPS_MTK.cpp
index 18db437027f..10b95572046 100644
--- a/libraries/AP_GPS/AP_GPS_MTK.cpp
+++ b/libraries/AP_GPS/AP_GPS_MTK.cpp
@@ -176,6 +176,7 @@ AP_GPS_MTK::_detect(struct MTK_detect_state &state, uint8_t data)
                 break;
             }
             state.step = 0;
+            FALLTHROUGH;
         case 0:
 			state.ck_b = state.ck_a = state.payload_counter = 0;
             if(PREAMBLE1 == data)
diff --git a/libraries/AP_GPS/AP_GPS_NMEA.cpp b/libraries/AP_GPS/AP_GPS_NMEA.cpp
index f8b4811cb9b..59b1f405fa1 100644
--- a/libraries/AP_GPS/AP_GPS_NMEA.cpp
+++ b/libraries/AP_GPS/AP_GPS_NMEA.cpp
@@ -140,7 +140,7 @@ bool AP_GPS_NMEA::_decode(char c)
     switch (c) {
     case ',': // term terminators
         _parity ^= c;
-        /* no break */
+        FALLTHROUGH;
     case '\r':
     case '\n':
     case '*':
diff --git a/libraries/AP_GPS/AP_GPS_SIRF.cpp b/libraries/AP_GPS/AP_GPS_SIRF.cpp
index 3abe84325ea..86893fde138 100644
--- a/libraries/AP_GPS/AP_GPS_SIRF.cpp
+++ b/libraries/AP_GPS/AP_GPS_SIRF.cpp
@@ -83,7 +83,7 @@ AP_GPS_SIRF::read(void)
                 break;
             }
             _step = 0;
-        // FALLTHROUGH
+            FALLTHROUGH;
         case 0:
             if(PREAMBLE1 == data)
                 _step++;
diff --git a/libraries/AP_GPS/AP_GPS_UBLOX.cpp b/libraries/AP_GPS/AP_GPS_UBLOX.cpp
index c6af586840d..f851987bc89 100644
--- a/libraries/AP_GPS/AP_GPS_UBLOX.cpp
+++ b/libraries/AP_GPS/AP_GPS_UBLOX.cpp
@@ -398,7 +398,7 @@ AP_GPS_UBLOX::read(void)
             }
             _step = 0;
             Debug("reset %u", __LINE__);
-            /* no break */
+            FALLTHROUGH;
         case 0:
             if(PREAMBLE1 == data)
                 _step++;
@@ -1215,7 +1215,7 @@ reset:
                 break;
             }
             state.step = 0;
-            /* no break */
+            FALLTHROUGH;
         case 0:
             if (PREAMBLE1 == data)
                 state.step++;