diff --git a/packages/mermaid/src/diagrams/flowchart/parser/flow-singlenode.spec.js b/packages/mermaid/src/diagrams/flowchart/parser/flow-singlenode.spec.js
index 8489ca725..59336d8d4 100644
--- a/packages/mermaid/src/diagrams/flowchart/parser/flow-singlenode.spec.js
+++ b/packages/mermaid/src/diagrams/flowchart/parser/flow-singlenode.spec.js
@@ -27,7 +27,7 @@ const keywords = [
   'subgraph',
 ];
 
-const specialChars = ['#', ':', '0', '&', ',', '*', '.', '\\', 'v', '-', '/'];
+const specialChars = ['#', ':', '0', '&', ',', '*', '.', '\\', 'v', '-', '/', '_'];
 
 describe('[Singlenodes] when parsing', () => {
   beforeEach(function () {