diff --git a/src/diagrams/flowchart/parser/flow.jison b/src/diagrams/flowchart/parser/flow.jison
index ff02bb4e1..27ac0c9de 100644
--- a/src/diagrams/flowchart/parser/flow.jison
+++ b/src/diagrams/flowchart/parser/flow.jison
@@ -552,7 +552,7 @@ alphaNumStatement
         {$$='-';}
     ;
 
-alphaNumToken  : PUNCTUATION | UNICODE_TEXT | NUM| ALPHA | COLON | COMMA | PLUS | EQUALS | MULT | DOT | BRKT ;
+alphaNumToken  : PUNCTUATION | UNICODE_TEXT | NUM| ALPHA | COLON | COMMA | PLUS | EQUALS | MULT | DOT | BRKT| UNDERSCORE ;
 
 idStringToken  : ALPHA|UNDERSCORE |UNICODE_TEXT | NUM|  COLON | COMMA | PLUS | MINUS | DOWN |EQUALS | MULT | BRKT | DOT | PUNCTUATION;
 
diff --git a/src/diagrams/flowchart/parser/flow.spec.js b/src/diagrams/flowchart/parser/flow.spec.js
index de2f71f8e..217a2a4c8 100644
--- a/src/diagrams/flowchart/parser/flow.spec.js
+++ b/src/diagrams/flowchart/parser/flow.spec.js
@@ -1158,6 +1158,15 @@ describe('when parsing ', function () {
     expect(vert['A'].type).toBe('square')
     expect(vert['A'].text).toBe('chimpansen hoppar')
   })
+  it('should handle text including _ in vertices', function () {
+    const res = flow.parser.parse('graph TD;A[chimpansen_hoppar] --> C;')
+
+    const vert = flow.parser.yy.getVertices()
+    const edges = flow.parser.yy.getEdges()
+
+    expect(vert['A'].type).toBe('square')
+    expect(vert['A'].text).toBe('chimpansen_hoppar')
+  })
 
   it('should handle quoted text in vertices ', function () {
     const res = flow.parser.parse('graph TD;A["chimpansen hoppar ()[]"] --> C;')
@@ -1613,6 +1622,22 @@ describe('when parsing ', function () {
     expect(classes['exClass'].styles[0]).toBe('background:#bbb')
     expect(classes['exClass'].styles[1]).toBe('border:1px solid red')
   })
+  it('should be possible to apply a class to a vertex with an id containing _', function () {
+    let statement = ''
+
+    statement = statement + 'graph TD;' + '\n'
+    statement = statement + 'classDef exClass background:#bbb,border:1px solid red;' + '\n'
+    statement = statement + 'a_a-->b_b;' + '\n'
+    statement = statement + 'class a_a exClass;'
+
+    const res = flow.parser.parse(statement)
+
+    const classes = flow.parser.yy.getClasses()
+
+    expect(classes['exClass'].styles.length).toBe(2)
+    expect(classes['exClass'].styles[0]).toBe('background:#bbb')
+    expect(classes['exClass'].styles[1]).toBe('border:1px solid red')
+  })
   it('should be possible to apply a class to a vertex directly', function () {
     let statement = ''