diff --git a/src/Environment/realwx_ctrl.cxx b/src/Environment/realwx_ctrl.cxx
index 03db5a87a..621fb11c3 100644
--- a/src/Environment/realwx_ctrl.cxx
+++ b/src/Environment/realwx_ctrl.cxx
@@ -40,6 +40,7 @@
 #include <simgear/threads/SGQueue.hxx>
 #endif
 
+using simgear::PropertyList;
 
 namespace Environment {