diff --git a/libraries/AP_Math/AP_Math.cpp b/libraries/AP_Math/AP_Math.cpp
index 000b79ddc4..d621fc2fe1 100644
--- a/libraries/AP_Math/AP_Math.cpp
+++ b/libraries/AP_Math/AP_Math.cpp
@@ -339,10 +339,12 @@ bool rotation_equal(enum Rotation r1, enum Rotation r2)
 }
 
 
+#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
 // fill an array of float with NaN, used to invalidate memory in SITL
 void fill_nanf(float *f, uint16_t count)
 {
     while (count--) {
-        *f++ = nanf("fill");
+        *f++ = std::numeric_limits<float>::signaling_NaN();
     }
 }
+#endif
diff --git a/libraries/AP_Math/AP_Math.h b/libraries/AP_Math/AP_Math.h
index fd560dc1b8..8d7b2c5365 100644
--- a/libraries/AP_Math/AP_Math.h
+++ b/libraries/AP_Math/AP_Math.h
@@ -277,5 +277,8 @@ Vector3f rand_vec3f(void);
 // return true if two rotations are equal
 bool rotation_equal(enum Rotation r1, enum Rotation r2) WARN_IF_UNUSED;
 
+#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
 // fill an array of float with NaN, used to invalidate memory in SITL
 void fill_nanf(float *f, uint16_t count);
+#endif
+