diff --git a/libraries/AP_Compass/AP_Compass_IST8310.cpp b/libraries/AP_Compass/AP_Compass_IST8310.cpp
index 779c953109..1ece7cfc1c 100644
--- a/libraries/AP_Compass/AP_Compass_IST8310.cpp
+++ b/libraries/AP_Compass/AP_Compass_IST8310.cpp
@@ -56,7 +56,7 @@
 #define PDCNTL_REG 0x42
 #define PDCNTL_VAL_PULSE_DURATION_NORMAL 0xC0
 
-#define SAMPLING_PERIOD_USEC (10 * USEC_PER_MSEC)
+#define SAMPLING_PERIOD_USEC (10 * AP_USEC_PER_MSEC)
 
 /*
  * FSR: