diff --git a/src/Aircraft/AircraftPerformance.hxx b/src/Aircraft/AircraftPerformance.hxx
index c2183de8a..fcf6878fa 100644
--- a/src/Aircraft/AircraftPerformance.hxx
+++ b/src/Aircraft/AircraftPerformance.hxx
@@ -18,6 +18,7 @@
 #ifndef AIRCRAFTPERFORMANCE_HXX
 #define AIRCRAFTPERFORMANCE_HXX
 
+#include <string>
 #include <vector>
 #include <functional>