diff --git a/xs/src/libslic3r/Polyline.cpp b/xs/src/libslic3r/Polyline.cpp
index ba41893f8..f56dd03b9 100644
--- a/xs/src/libslic3r/Polyline.cpp
+++ b/xs/src/libslic3r/Polyline.cpp
@@ -157,6 +157,7 @@ Polyline::simplify_by_visibility(const T &area)
         }
     }
 }
+template void Polyline::simplify_by_visibility<ExPolygon>(const ExPolygon &area);
 template void Polyline::simplify_by_visibility<ExPolygonCollection>(const ExPolygonCollection &area);
 
 void