diff --git a/simgear/structure/SGExpression.cxx b/simgear/structure/SGExpression.cxx
index 2633e311..e6b38500 100644
--- a/simgear/structure/SGExpression.cxx
+++ b/simgear/structure/SGExpression.cxx
@@ -33,6 +33,7 @@
 #include <sstream>
 #include <boost/bind.hpp>
 #include <cstring> // for strcmp
+#include <cassert>
 
 #include <simgear/props/props.hxx>
 
diff --git a/simgear/structure/subsystem_mgr.cxx b/simgear/structure/subsystem_mgr.cxx
index bd990546..92daefcf 100644
--- a/simgear/structure/subsystem_mgr.cxx
+++ b/simgear/structure/subsystem_mgr.cxx
@@ -21,6 +21,7 @@
 #include <simgear_config.h>
 
 #include <algorithm>
+#include <cassert>
 
 #include <simgear/debug/logstream.hxx>
 #include <simgear/timing/timestamp.hxx>