diff --git a/packages/mermaid/src/diagrams/flowchart/flowDb.ts b/packages/mermaid/src/diagrams/flowchart/flowDb.ts
index e321f3a0b..1105c9ef3 100644
--- a/packages/mermaid/src/diagrams/flowchart/flowDb.ts
+++ b/packages/mermaid/src/diagrams/flowchart/flowDb.ts
@@ -820,13 +820,13 @@ const getTypeFromVertex = (vertex: FlowVertex) => {
     return 'imageSquare';
   }
   if (vertex?.icon) {
-    if (vertex.form === 'circle') {
+    if (vertex?.form === 'circle') {
       return 'iconCircle';
     }
-    if (vertex.form === 'square') {
+    if (vertex?.form === 'square') {
       return 'iconSquare';
     }
-    if (vertex.form === 'rounded') {
+    if (vertex?.form === 'rounded') {
       return 'iconRounded';
     }
     return 'icon';