diff --git a/window/demo/Window_stream/makefile b/window/demo/Window_stream/makefile
index e0a82a16a0a..f71f58b77e5 100644
--- a/window/demo/Window_stream/makefile
+++ b/window/demo/Window_stream/makefile
@@ -45,6 +45,6 @@ clean: \
 #                    suffix rules
 #---------------------------------------------------------------------#
 
-.C$(OBJ_EXT):
+.cpp$(OBJ_EXT):
 	$(CGAL_CXX) $(CXXFLAGS) $(OBJ_OPT) $<
 
diff --git a/window/demo/Window_stream/window_input.C b/window/demo/Window_stream/window_input.cpp
similarity index 100%
rename from window/demo/Window_stream/window_input.C
rename to window/demo/Window_stream/window_input.cpp