diff --git a/Constrained_triangulation_3/include/CGAL/Constrained_Delaunay_triangulation_3.h b/Constrained_triangulation_3/include/CGAL/Constrained_Delaunay_triangulation_3.h
index 5c1b06124d6..a40c78469f1 100644
--- a/Constrained_triangulation_3/include/CGAL/Constrained_Delaunay_triangulation_3.h
+++ b/Constrained_triangulation_3/include/CGAL/Constrained_Delaunay_triangulation_3.h
@@ -72,7 +72,7 @@
 #  error "Compiler needs <format>"
 #endif
 
-#if 0
+#ifndef DOXYGEN_RUNNING
 
 namespace CGAL {
 
@@ -171,8 +171,6 @@ namespace CGAL {
 
 } // end namespace CGAL
 
-#else // not DOXYGEN_RUNNING
-
 namespace CGAL {
 
 template <class K>
@@ -3529,6 +3527,6 @@ protected:
 
 } // end CGAL
 
-#endif // not DOXYGEN_RUNNING
+#endif // DOXYGEN_RUNNING
 
 #endif // CGAL_CONSTRAINED_DELAUNAY_TRIANGULATION_3_H