diff --git a/simgear/timing/sg_time.cxx b/simgear/timing/sg_time.cxx
index 0013d3b0..e10400c3 100644
--- a/simgear/timing/sg_time.cxx
+++ b/simgear/timing/sg_time.cxx
@@ -91,6 +91,7 @@ SGTime::SGTime( double lon, double lat, const string& root )
 	// cout << "Using zonename = " << zonename << endl;
     } else {
 	tzContainer = NULL;
+	zonename = NULL;
     }
 }