diff --git a/packages/mermaid/src/rendering-util/layout-algorithms/fixed/index.js b/packages/mermaid/src/rendering-util/layout-algorithms/fixed/index.js
index 52f8e921c..aa668d834 100644
--- a/packages/mermaid/src/rendering-util/layout-algorithms/fixed/index.js
+++ b/packages/mermaid/src/rendering-util/layout-algorithms/fixed/index.js
@@ -265,8 +265,8 @@ const doRender = async (_elem, data4Layout, siteConfig, positions) => {
   await Promise.all(
     data4Layout.nodes.map(async function (node) {
       let pos = positions.nodes[node.id];
-      node.height = pos?.height;
-      node.width = pos?.width;
+      node.height = pos?.height || 0;
+      node.width = pos?.width || 0;
 
       if (node.isGroup) {
         node.x = 0;