diff --git a/gridmesh.h b/gridmesh.h
index 6c447c1..ff07f99 100644
--- a/gridmesh.h
+++ b/gridmesh.h
@@ -6,7 +6,7 @@
 class GridMesh : public MeshBuilder
 {
 public:
-    GridMesh(int width, int height, bool alternate);
+    GridMesh(int width, int height, bool alternate = true);
 private:
 	int getVertexId(int i, int j, int height);
 };