diff --git a/src/AIModel/performancedb.cxx b/src/AIModel/performancedb.cxx
index 3f9aafa68..f7c286a9a 100644
--- a/src/AIModel/performancedb.cxx
+++ b/src/AIModel/performancedb.cxx
@@ -1,3 +1,4 @@
+#include <simgear/math/SGMath.hxx>
 #include <simgear/misc/sg_path.hxx>
 #include <simgear/props/props.hxx>
 #include <simgear/props/props_io.hxx>
diff --git a/src/Input/FGDeviceConfigurationMap.cxx b/src/Input/FGDeviceConfigurationMap.cxx
index 413222f04..431a6fa5e 100644
--- a/src/Input/FGDeviceConfigurationMap.cxx
+++ b/src/Input/FGDeviceConfigurationMap.cxx
@@ -26,6 +26,8 @@
 #  include <config.h>
 #endif
 
+#include <simgear/math/SGMath.hxx>
+
 #include "FGDeviceConfigurationMap.hxx"
 
 #include <plib/ul.h>