diff --git a/libraries/AP_Compass/AP_Compass_IST8308.cpp b/libraries/AP_Compass/AP_Compass_IST8308.cpp
index e1031a1960..722457dda3 100644
--- a/libraries/AP_Compass/AP_Compass_IST8308.cpp
+++ b/libraries/AP_Compass/AP_Compass_IST8308.cpp
@@ -168,7 +168,7 @@ bool AP_Compass_IST8308::init()
     set_dev_id(_instance, _dev->get_bus_id());
 
     printf("%s found on bus %u id %u address 0x%02x\n", name,
-           _dev->bus_num(), _dev->get_bus_id(), _dev->get_bus_address());
+           _dev->bus_num(), unsigned(_dev->get_bus_id()), _dev->get_bus_address());
 
     set_rotation(_instance, _rotation);
 
diff --git a/libraries/AP_Compass/AP_Compass_IST8310.cpp b/libraries/AP_Compass/AP_Compass_IST8310.cpp
index c391ed5083..75c0ab8e17 100644
--- a/libraries/AP_Compass/AP_Compass_IST8310.cpp
+++ b/libraries/AP_Compass/AP_Compass_IST8310.cpp
@@ -178,7 +178,7 @@ bool AP_Compass_IST8310::init()
     set_dev_id(_instance, _dev->get_bus_id());
 
     printf("%s found on bus %u id %u address 0x%02x\n", name,
-           _dev->bus_num(), _dev->get_bus_id(), _dev->get_bus_address());
+           _dev->bus_num(), unsigned(_dev->get_bus_id()), _dev->get_bus_address());
 
     set_rotation(_instance, _rotation);
 
diff --git a/libraries/AP_Compass/AP_Compass_LIS3MDL.cpp b/libraries/AP_Compass/AP_Compass_LIS3MDL.cpp
index 7c6efbb6b3..b43f0706e1 100644
--- a/libraries/AP_Compass/AP_Compass_LIS3MDL.cpp
+++ b/libraries/AP_Compass/AP_Compass_LIS3MDL.cpp
@@ -113,7 +113,7 @@ bool AP_Compass_LIS3MDL::init()
     }
     set_dev_id(compass_instance, dev->get_bus_id());
 
-    printf("Found a LIS3MDL on 0x%x as compass %u\n", dev->get_bus_id(), compass_instance);
+    printf("Found a LIS3MDL on 0x%x as compass %u\n", unsigned(dev->get_bus_id()), compass_instance);
     
     set_rotation(compass_instance, rotation);
 
diff --git a/libraries/AP_Compass/AP_Compass_MMC3416.cpp b/libraries/AP_Compass/AP_Compass_MMC3416.cpp
index aab22e046a..f58b779e31 100644
--- a/libraries/AP_Compass/AP_Compass_MMC3416.cpp
+++ b/libraries/AP_Compass/AP_Compass_MMC3416.cpp
@@ -99,7 +99,7 @@ bool AP_Compass_MMC3416::init()
     
     set_dev_id(compass_instance, dev->get_bus_id());
 
-    printf("Found a MMC3416 on 0x%x as compass %u\n", dev->get_bus_id(), compass_instance);
+    printf("Found a MMC3416 on 0x%x as compass %u\n", unsigned(dev->get_bus_id()), compass_instance);
     
     set_rotation(compass_instance, rotation);
 
diff --git a/libraries/AP_Compass/AP_Compass_MMC5xx3.cpp b/libraries/AP_Compass/AP_Compass_MMC5xx3.cpp
index fdde08bfca..2e6c1c0a88 100644
--- a/libraries/AP_Compass/AP_Compass_MMC5xx3.cpp
+++ b/libraries/AP_Compass/AP_Compass_MMC5xx3.cpp
@@ -115,7 +115,7 @@ bool AP_Compass_MMC5XX3::init()
 
     set_dev_id(compass_instance, dev->get_bus_id());
 
-    printf("Found a MMC5983 on 0x%x as compass %u\n", dev->get_bus_id(), compass_instance);
+    printf("Found a MMC5983 on 0x%x as compass %u\n", unsigned(dev->get_bus_id()), compass_instance);
 
     set_rotation(compass_instance, rotation);
 
diff --git a/libraries/AP_Compass/AP_Compass_QMC5883L.cpp b/libraries/AP_Compass/AP_Compass_QMC5883L.cpp
index aabed388dc..5414cedb28 100644
--- a/libraries/AP_Compass/AP_Compass_QMC5883L.cpp
+++ b/libraries/AP_Compass/AP_Compass_QMC5883L.cpp
@@ -123,7 +123,7 @@ bool AP_Compass_QMC5883L::init()
     set_dev_id(_instance, _dev->get_bus_id());
 
     printf("%s found on bus %u id %u address 0x%02x\n", name,
-           _dev->bus_num(), _dev->get_bus_id(), _dev->get_bus_address());
+           _dev->bus_num(), unsigned(_dev->get_bus_id()), _dev->get_bus_address());
 
     set_rotation(_instance, _rotation);
 
diff --git a/libraries/AP_Compass/AP_Compass_QMC5883P.cpp b/libraries/AP_Compass/AP_Compass_QMC5883P.cpp
index af8e6861ae..fb84afdd3e 100644
--- a/libraries/AP_Compass/AP_Compass_QMC5883P.cpp
+++ b/libraries/AP_Compass/AP_Compass_QMC5883P.cpp
@@ -134,7 +134,7 @@ bool AP_Compass_QMC5883P::init()
     set_dev_id(_instance, _dev->get_bus_id());
 
     printf("%s found on bus %u id %u address 0x%02x\n", name,
-           _dev->bus_num(), _dev->get_bus_id(), _dev->get_bus_address());
+           _dev->bus_num(), unsigned(_dev->get_bus_id()), _dev->get_bus_address());
 
     set_rotation(_instance, _rotation);