diff --git a/src/Lib/Polygon/tg_unique_geod.hxx b/src/Lib/Polygon/tg_unique_geod.hxx
index 293e53cf..78926792 100644
--- a/src/Lib/Polygon/tg_unique_geod.hxx
+++ b/src/Lib/Polygon/tg_unique_geod.hxx
@@ -1,4 +1,5 @@
 #include <boost/unordered_set.hpp>
+#include <simgear/math/SGMisc.hxx>
 
 // Implement Unique SGGeod list
 
@@ -41,8 +42,8 @@ public:
 
         /* only hash lon, lat - we want to detect dups in 2d only */
         unsigned long long raw_pt[2];
-        raw_pt[0] = (unsigned long long)( round(geod.getLongitudeDeg() * PROXIMITY_MULTIPLIER) );
-        raw_pt[1] = (unsigned long long)( round(geod.getLatitudeDeg() * PROXIMITY_MULTIPLIER) );
+        raw_pt[0] = (unsigned long long)( SGMisc::round(geod.getLongitudeDeg() * PROXIMITY_MULTIPLIER) );
+        raw_pt[1] = (unsigned long long)( SGMisc::round(geod.getLatitudeDeg() * PROXIMITY_MULTIPLIER) );
 
         unsigned char* it = (unsigned char*)raw_pt;
         for ( unsigned i=0; i<sizeof( raw_pt ); i++ ) {
@@ -122,4 +123,4 @@ public:
 private:
     unique_geod_set         index_list;
     std::vector<SGGeod>     geod_list;
-};
\ No newline at end of file
+};