diff --git a/libraries/Filter/NotchFilter.cpp b/libraries/Filter/NotchFilter.cpp
index dbbec6f80a802..3c9a620d6c3f7 100644
--- a/libraries/Filter/NotchFilter.cpp
+++ b/libraries/Filter/NotchFilter.cpp
@@ -19,6 +19,7 @@
 #endif
 
 #include "NotchFilter.h"
+#include <AP_Logger/AP_Logger.h>
 
 const static float NOTCH_MAX_SLEW       = 0.05f;
 const static float NOTCH_MAX_SLEW_LOWER = 1.0f - NOTCH_MAX_SLEW;
@@ -135,6 +136,15 @@ void NotchFilter<T>::reset()
     need_reset = true;
 }
 
+#if HAL_LOGGING_ENABLED
+// return the frequency to log for the notch
+template <class T>
+float NotchFilter<T>::logging_frequency() const
+{
+    return initialised ? _center_freq_hz : AP::logger().quiet_nanf();
+}
+#endif
+
 /*
    instantiate template classes
  */
diff --git a/libraries/Filter/NotchFilter.h b/libraries/Filter/NotchFilter.h
index 9f2e49c66acb6..811f7800fccf5 100644
--- a/libraries/Filter/NotchFilter.h
+++ b/libraries/Filter/NotchFilter.h
@@ -49,9 +49,7 @@ class NotchFilter {
     }
 
     // return the frequency to log for the notch
-    float logging_frequency(void) const {
-        return initialised?_center_freq_hz:0;
-    }
+    float logging_frequency(void) const;
 
 protected: