diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index f6396e8f7..abfa87a75 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -2812,7 +2812,7 @@ std::string GCode::extrude_infill(const Print &print, const std::vector<ObjectBy
 //        for (ExtrusionEntity *fill : ExtrusionEntityCollection::chained_path_from(region.infills, m_last_pos).entities) {
         // Don't sort the infills, they contain gap fill, which shall be extruded after normal fills.
         for (const ExtrusionEntity *fill : region.infills) {
-            auto *eec = dynamic_cast<ExtrusionEntityCollection*>(fill);
+            auto *eec = dynamic_cast<const ExtrusionEntityCollection*>(fill);
             if (eec) {
 				for (ExtrusionEntity *ee : eec->chained_path_from(m_last_pos).entities)
                     gcode += this->extrude_entity(*ee, "infill");