diff --git a/tests/tools/visualization/test_graph.py b/tests/tools/visualization/test_graph.py
index ba47b335b2..6ffe491420 100644
--- a/tests/tools/visualization/test_graph.py
+++ b/tests/tools/visualization/test_graph.py
@@ -353,6 +353,7 @@ def test_graph_node_identifiers(self, node_id_type, monkeypatch, file_regression
         # The order of certain output lines can be randomly ordered so we split the file in lines, sort, and then join
         # them into a single string again. The node identifiers generated by the engine are of the form ``N{pk}`` and
         # they also clearly vary, so they are replaced with the ``NODE`` placeholder.
-        string = '\n'.join(sorted(graph.graphviz.source.strip().split('\n')))
+        string = graph.graphviz.source
         string = re.sub(r'N\d+', 'NODE', string)
+        string = '\n'.join(sorted(string.strip().split('\n')))
         file_regression.check(string)