diff --git a/libraries/AP_Compass/AP_Compass.cpp b/libraries/AP_Compass/AP_Compass.cpp
index 517d98ee6a..3501ebd17c 100644
--- a/libraries/AP_Compass/AP_Compass.cpp
+++ b/libraries/AP_Compass/AP_Compass.cpp
@@ -2066,6 +2066,11 @@ bool Compass::consistent() const
     return true;
 }
 
+bool Compass::healthy(uint8_t i) const
+{
+    return (i < COMPASS_MAX_INSTANCES) ? _get_state(Priority(i)).healthy : false;
+}
+
 /*
   return true if we have a valid scale factor
  */
diff --git a/libraries/AP_Compass/AP_Compass.h b/libraries/AP_Compass/AP_Compass.h
index 53d760404d..609ee970b5 100644
--- a/libraries/AP_Compass/AP_Compass.h
+++ b/libraries/AP_Compass/AP_Compass.h
@@ -205,7 +205,7 @@ public:
     bool consistent() const;
 
     /// Return the health of a compass
-    bool healthy(uint8_t i) const { return _get_state(Priority(i)).healthy; }
+    bool healthy(uint8_t i) const;
     bool healthy(void) const { return healthy(_first_usable); }
     uint8_t get_healthy_mask() const;