diff --git a/libraries/AP_Compass/AP_Compass.cpp b/libraries/AP_Compass/AP_Compass.cpp
index 9d5f2e8101..f31655cdfb 100644
--- a/libraries/AP_Compass/AP_Compass.cpp
+++ b/libraries/AP_Compass/AP_Compass.cpp
@@ -1251,7 +1251,7 @@ void Compass::_probe_external_i2c_compasses(void)
 #endif
 #endif
 
-#if AP_COMPASS_BMM150_ENABLED
+#if AP_COMPASS_BMM150_DETECT_BACKENDS_ENABLED
     // BMM150 on I2C
     FOREACH_I2C_EXTERNAL(i) {
         for (uint8_t addr=BMM150_I2C_ADDR_MIN; addr <= BMM150_I2C_ADDR_MAX; addr++) {
diff --git a/libraries/AP_Compass/AP_Compass_config.h b/libraries/AP_Compass/AP_Compass_config.h
index eabbe9de1b..28043bc619 100644
--- a/libraries/AP_Compass/AP_Compass_config.h
+++ b/libraries/AP_Compass/AP_Compass_config.h
@@ -42,6 +42,15 @@
 #define AP_COMPASS_BMM150_ENABLED AP_COMPASS_I2C_BACKEND_DEFAULT_ENABLED && !defined(STM32F1)
 #endif
 
+// this define dictates whether we iterate over the external i2c
+// busses looking for BMM150.  Ordinarily this should be true, but
+// SkyViper specifies its BMM150 and thus does not need to probe.
+// This is an interim arrangement until PCNC1 is eliminated as an
+// auto-detect board.
+#ifndef AP_COMPASS_BMM150_DETECT_BACKENDS_ENABLED
+#define AP_COMPASS_BMM150_DETECT_BACKENDS_ENABLED AP_COMPASS_BMM150_ENABLED
+#endif
+
 #ifndef AP_COMPASS_HMC5843_ENABLED
 #define AP_COMPASS_HMC5843_ENABLED AP_COMPASS_I2C_BACKEND_DEFAULT_ENABLED
 #endif