diff --git a/libraries/AP_Compass/AP_Compass_HMC5843.cpp b/libraries/AP_Compass/AP_Compass_HMC5843.cpp
index c7f061b950..04bded5228 100644
--- a/libraries/AP_Compass/AP_Compass_HMC5843.cpp
+++ b/libraries/AP_Compass/AP_Compass_HMC5843.cpp
@@ -108,7 +108,7 @@ AP_Compass_HMC5843::init()
 	  calibration_gain = 0x60;
 	  expected_xy = 766;
 	  expected_z  = 713;
-  } else if (base_config == NormalOperation | DataOutputRate_75HZ<<2) {
+  } else if (base_config == (NormalOperation | DataOutputRate_75HZ<<2)) {
       product_id = AP_COMPASS_TYPE_HMC5843;
   } else {
 	 // not behaving like either supported compass type