diff --git a/src/BuildTiles/GenOutput/genobj.cxx b/src/BuildTiles/GenOutput/genobj.cxx
index 9ca04ac2..d9b029f8 100644
--- a/src/BuildTiles/GenOutput/genobj.cxx
+++ b/src/BuildTiles/GenOutput/genobj.cxx
@@ -212,7 +212,7 @@ int FGGenOutput::build( FGConstruct& c ) {
 
 // caclulate the bounding sphere for a list of triangle faces
 void FGGenOutput::calc_group_bounding_sphere( FGConstruct& c, 
-					      const fan_list& fans, 
+					      const opt_list& fans, 
 					      Point3D *center, double *radius )
 {
     cout << "calculate group bounding sphere for " << fans.size() << " fans." 
@@ -223,8 +223,8 @@ void FGGenOutput::calc_group_bounding_sphere( FGConstruct& c,
     // generate a list of unique points from the triangle list
     FGTriNodes nodes;
 
-    const_fan_list_iterator f_current = fans.begin();
-    const_fan_list_iterator f_last = fans.end();
+    const_opt_list_iterator f_current = fans.begin();
+    const_opt_list_iterator f_last = fans.end();
     for ( ; f_current != f_last; ++f_current ) {
 	const_int_list_iterator i_current = f_current->begin();
 	const_int_list_iterator i_last = f_current->end();
diff --git a/src/BuildTiles/GenOutput/genobj.hxx b/src/BuildTiles/GenOutput/genobj.hxx
index 5cb12641..75e34fc1 100644
--- a/src/BuildTiles/GenOutput/genobj.hxx
+++ b/src/BuildTiles/GenOutput/genobj.hxx
@@ -66,7 +66,7 @@ private:
     FGTriNodes tex_coords;
 
     // fan list
-    fan_list fans[FG_MAX_AREA_TYPES];
+    opt_list fans[FG_MAX_AREA_TYPES];
 
     // textures pointer list
     tex_list textures[FG_MAX_AREA_TYPES];
@@ -80,7 +80,7 @@ private:
     void calc_gbs( FGConstruct& c );
 
     // caclulate the bounding sphere for a list of triangle faces
-    void calc_group_bounding_sphere( FGConstruct& c, const fan_list& fans, 
+    void calc_group_bounding_sphere( FGConstruct& c, const opt_list& fans, 
 				     Point3D *center, double *radius );
 
     // caclulate the bounding sphere for the specified triangle face