diff --git a/Convex_hull_2/demo/Convex_hull_2/Qt_widget_move_list_point.C b/Convex_hull_2/demo/Convex_hull_2/Qt_widget_move_list_point.cpp
similarity index 100%
rename from Convex_hull_2/demo/Convex_hull_2/Qt_widget_move_list_point.C
rename to Convex_hull_2/demo/Convex_hull_2/Qt_widget_move_list_point.cpp
diff --git a/Convex_hull_2/demo/Convex_hull_2/Qt_widget_toolbar.C b/Convex_hull_2/demo/Convex_hull_2/Qt_widget_toolbar.cpp
similarity index 100%
rename from Convex_hull_2/demo/Convex_hull_2/Qt_widget_toolbar.C
rename to Convex_hull_2/demo/Convex_hull_2/Qt_widget_toolbar.cpp
diff --git a/Convex_hull_2/demo/Convex_hull_2/convex_hull_2.C b/Convex_hull_2/demo/Convex_hull_2/convex_hull_2.cpp
similarity index 100%
rename from Convex_hull_2/demo/Convex_hull_2/convex_hull_2.C
rename to Convex_hull_2/demo/Convex_hull_2/convex_hull_2.cpp
diff --git a/Convex_hull_2/demo/Convex_hull_2/makefile b/Convex_hull_2/demo/Convex_hull_2/makefile
index f3fcbb9908a..5dc7afba12a 100644
--- a/Convex_hull_2/demo/Convex_hull_2/makefile
+++ b/Convex_hull_2/demo/Convex_hull_2/makefile
@@ -36,23 +36,23 @@ LDFLAGS = \
 
 all: convex_hull_2
 
-Qt_widget_toolbar$(OBJ_EXT): Qt_widget_toolbar.C Qt_widget_toolbar.moc
-	$(CGAL_CXX) $(CXXFLAGS) $(OBJ_OPT) Qt_widget_toolbar.C
+Qt_widget_toolbar$(OBJ_EXT): Qt_widget_toolbar.cpp Qt_widget_toolbar.moc
+	$(CGAL_CXX) $(CXXFLAGS) $(OBJ_OPT) Qt_widget_toolbar.cpp
 
 Qt_widget_toolbar.moc: Qt_widget_toolbar.h
 	$(QT_MOC) -o Qt_widget_toolbar.moc Qt_widget_toolbar.h
 
 Qt_widget_move_list_point$(OBJ_EXT): Qt_widget_move_list_point.moc \
-					Qt_widget_move_list_point.C
-	$(CGAL_CXX) $(CXXFLAGS) $(OBJ_OPT) Qt_widget_move_list_point.C
+					Qt_widget_move_list_point.cpp
+	$(CGAL_CXX) $(CXXFLAGS) $(OBJ_OPT) Qt_widget_move_list_point.cpp
 Qt_widget_move_list_point.moc: Qt_widget_move_list_point.h
 	$(QT_MOC) -o Qt_widget_move_list_point.moc Qt_widget_move_list_point.h
 
-convex_hull_2.moc: convex_hull_2.C Qt_widget_toolbar$(OBJ_EXT) 
-	${QT_MOC} -o convex_hull_2.moc convex_hull_2.C
+convex_hull_2.moc: convex_hull_2.cpp Qt_widget_toolbar$(OBJ_EXT) 
+	${QT_MOC} -o convex_hull_2.moc convex_hull_2.cpp
 
-convex_hull_2$(OBJ_EXT): convex_hull_2.C convex_hull_2.moc
-	$(CGAL_CXX) $(CXXFLAGS) $(OBJ_OPT) convex_hull_2.C
+convex_hull_2$(OBJ_EXT): convex_hull_2.cpp convex_hull_2.moc
+	$(CGAL_CXX) $(CXXFLAGS) $(OBJ_OPT) convex_hull_2.cpp
 
 convex_hull_2$(EXE_EXT): convex_hull_2$(OBJ_EXT) \
 			 Qt_widget_move_list_point$(OBJ_EXT)
@@ -68,5 +68,5 @@ clean: convex_hull_2.clean \
 #                    suffix rules
 #---------------------------------------------------------------------#
 
-.C$(OBJ_EXT):
+.cpp$(OBJ_EXT):
 	$(CGAL_CXX) $(CXXFLAGS) $(OBJ_OPT) $<