diff --git a/packages/mermaid/src/dagre-wrapper/nodes.js b/packages/mermaid/src/dagre-wrapper/nodes.js
index b30084e90..1e1fbd41e 100644
--- a/packages/mermaid/src/dagre-wrapper/nodes.js
+++ b/packages/mermaid/src/dagre-wrapper/nodes.js
@@ -918,8 +918,8 @@ const class_box = (parent, node) => {
         ')'
     );
     //get the height of the bounding box of each member if exists
-    const memberBBox = lbl ? lbl.getBBox() : null;
-    verticalPos += (memberBBox.height ?? 0) + rowPadding;
+    const memberBBox = lbl?.getBBox();
+    verticalPos += (memberBBox?.height ?? 0) + rowPadding;
   });
 
   verticalPos += lineHeight;