diff --git a/src/ifcgeom/mapping/IfcDerivedProfileDef.cpp b/src/ifcgeom/mapping/IfcDerivedProfileDef.cpp
index 18091d3d2c..663680e29d 100644
--- a/src/ifcgeom/mapping/IfcDerivedProfileDef.cpp
+++ b/src/ifcgeom/mapping/IfcDerivedProfileDef.cpp
@@ -1,20 +1,20 @@
 /********************************************************************************
- *                                                                              *
- * This file is part of IfcOpenShell.                                           *
- *                                                                              *
- * IfcOpenShell is free software: you can redistribute it and/or modify         *
+ *																			  *
+ * This file is part of IfcOpenShell.										   *
+ *																			  *
+ * IfcOpenShell is free software: you can redistribute it and/or modify		 *
  * it under the terms of the Lesser GNU General Public License as published by  *
- * the Free Software Foundation, either version 3.0 of the License, or          *
- * (at your option) any later version.                                          *
- *                                                                              *
- * IfcOpenShell is distributed in the hope that it will be useful,              *
- * but WITHOUT ANY WARRANTY; without even the implied warranty of               *
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                 *
- * Lesser GNU General Public License for more details.                          *
- *                                                                              *
- * You should have received a copy of the Lesser GNU General Public License     *
- * along with this program. If not, see <http://www.gnu.org/licenses/>.         *
- *                                                                              *
+ * the Free Software Foundation, either version 3.0 of the License, or		  *
+ * (at your option) any later version.										  *
+ *																			  *
+ * IfcOpenShell is distributed in the hope that it will be useful,			  *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of			   *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the				 *
+ * Lesser GNU General Public License for more details.						  *
+ *																			  *
+ * You should have received a copy of the Lesser GNU General Public License	 *
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.		 *
+ *																			  *
  ********************************************************************************/
 
 #include "mapping.h"
@@ -28,7 +28,23 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcDerivedProfileDef* inst) {
 	}
 	// @todo we mutate it so we need to clone otherwise we alter the cached item.
 	it = taxonomy::item::ptr(it->clone_());
-	taxonomy::matrix4::ptr m = taxonomy::cast<taxonomy::matrix4>(map(inst->Operator()));
+
+	taxonomy::matrix4::ptr m;
+	bool is_mirror = false;
+#ifdef SCHEMA_HAS_IfcMirroredProfileDef
+	if (inst->as<IfcSchema::IfcMirroredProfileDef>()) {
+		m = taxonomy::make<taxonomy::matrix4>();
+		// @todo test
+		m->components().col(0) *= -1.;
+		is_mirror = true;
+	}
+#endif
+	if (!is_mirror) {
+		m = taxonomy::cast<taxonomy::matrix4>(map(inst->Operator()));
+		if (!m) {
+			return nullptr;
+		}
+	}
 	if (!taxonomy::cast<taxonomy::geom_item>(it)->matrix) {
 		// @todo should this not be initialized by default? matrix4 already has a 'lazy identity' mechanism.
 		taxonomy::cast<taxonomy::geom_item>(it)->matrix = taxonomy::make<taxonomy::matrix4>();