diff --git a/src/csgops.cc b/src/csgops.cc
index 508eeccf..ae970854 100644
--- a/src/csgops.cc
+++ b/src/csgops.cc
@@ -30,6 +30,8 @@
 #include "printutils.h"
 #ifdef ENABLE_CGAL
 #  include "cgal.h"
+#  include <CGAL/assertions_behaviour.h>
+#  include <CGAL/exceptions.h>
 #endif
 
 enum csg_type_e {
@@ -82,8 +84,10 @@ CGAL_Nef_polyhedron CsgNode::render_cgal_nef_polyhedron() const
 
 	print_messages_push();
 
+	CGAL::Failure_behaviour old_behaviour = CGAL::set_error_behaviour(CGAL::THROW_EXCEPTION);
 	bool first = true;
 	CGAL_Nef_polyhedron N;
+	try {
 	foreach (AbstractNode *v, children) {
 		if (v->modinst->tag_background)
 			continue;
@@ -110,8 +114,13 @@ CGAL_Nef_polyhedron CsgNode::render_cgal_nef_polyhedron() const
 		}
 		v->progress_report();
 	}
-
 	cgal_nef_cache.insert(cache_id, new cgal_nef_cache_entry(N), N.weight());
+	}
+	catch (CGAL::Assertion_exception e) {
+		PRINTF("ERROR: Illegal polygonal object - make sure all polygons are defined with the same winding order. Skipping affected object.");
+	}
+	CGAL::set_error_behaviour(old_behaviour);
+
 	print_messages_pop();
 	progress_report();
 
diff --git a/src/polyset.cc b/src/polyset.cc
index b8e77f42..47d858cc 100644
--- a/src/polyset.cc
+++ b/src/polyset.cc
@@ -667,6 +667,7 @@ CGAL_Nef_polyhedron PolySet::render_cgal_nef_polyhedron() const
 			CGAL::set_error_behaviour(old_behaviour);
 			return CGAL_Nef_polyhedron();
 		}
+		CGAL::set_error_behaviour(old_behaviour);
 	}
 	return CGAL_Nef_polyhedron();
 }
diff --git a/src/projection.cc b/src/projection.cc
index 1fb036cf..7a3f77a5 100644
--- a/src/projection.cc
+++ b/src/projection.cc
@@ -34,6 +34,11 @@
 #include "export.h"
 #include "progress.h"
 
+#ifdef ENABLE_CGAL
+#  include <CGAL/assertions_behaviour.h>
+#  include <CGAL/exceptions.h>
+#endif
+
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ -106,17 +111,26 @@ PolySet *ProjectionNode::render_polyset(render_mode_e) const
 
 	print_messages_push();
 
+	PolySet *ps = new PolySet();
+	ps->convexity = this->convexity;
+	ps->is2d = true;
+
 	CGAL_Nef_polyhedron N;
 	N.dim = 3;
+	CGAL::Failure_behaviour old_behaviour = CGAL::set_error_behaviour(CGAL::THROW_EXCEPTION);
+  try {
 	foreach(AbstractNode *v, this->children) {
 		if (v->modinst->tag_background)
 			continue;
 		N.p3 += v->render_cgal_nef_polyhedron().p3;
 	}
-
-	PolySet *ps = new PolySet();
-	ps->convexity = this->convexity;
-	ps->is2d = true;
+  }
+  catch (CGAL::Assertion_exception e) {
+		PRINTF("ERROR: Illegal polygonal object - make sure all polygons are defined with the same winding order. Skipping affected object.");
+		CGAL::set_error_behaviour(old_behaviour);
+		return ps;
+	}
+  CGAL::set_error_behaviour(old_behaviour);
 
 	if (cut_mode)
 	{