diff --git a/examples/guard_factorial_1.svg b/examples/guard_factorial_1.svg
index a7ff0a5..10284ed 100644
--- a/examples/guard_factorial_1.svg
+++ b/examples/guard_factorial_1.svg
@@ -1,3 +1,3 @@
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+ "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
\ No newline at end of file