diff --git a/components/zerodop/GPUtopozero/src/AkimaLib.cpp b/components/zerodop/GPUtopozero/src/AkimaLib.cpp
index 2a4b0e2..7f4ce8e 100644
--- a/components/zerodop/GPUtopozero/src/AkimaLib.cpp
+++ b/components/zerodop/GPUtopozero/src/AkimaLib.cpp
@@ -16,6 +16,7 @@
 using std::max;
 using std::min;
 using std::vector;
+using std::isnan;
 
 bool AkimaLib::aki_almostEqual(double x, double y) {
     bool ret = (abs(x - y) <= AKI_EPS) ? true : false; // Compressed version is a little cleaner