diff --git a/EKF/ekf.cpp b/EKF/ekf.cpp
index f9d90e9465..9826627baa 100644
--- a/EKF/ekf.cpp
+++ b/EKF/ekf.cpp
@@ -43,7 +43,7 @@
 #include "mathlib.h"
 
 #ifndef __PX4_QURT
-#if defined(__cplusplus)
+#if defined(__cplusplus) && !defined(__PX4_NUTTX)
 #include <cmath>
 #define ISFINITE(x) std::isfinite(x)
 #else