diff --git a/src/hooks/useVisibleEdges.ts b/src/hooks/useVisibleEdges.ts
index 5ab023d5..204dfe40 100644
--- a/src/hooks/useVisibleEdges.ts
+++ b/src/hooks/useVisibleEdges.ts
@@ -3,12 +3,15 @@ import { useCallback } from 'react';
 import { useStore } from '../store';
 import { isEdgeVisible } from '../container/EdgeRenderer/utils';
 import { ReactFlowState, NodeInternals, Edge } from '../types';
+import { isNumeric } from '../utils';
 
 function groupEdgesByZLevel(edges: Edge[], nodeInternals: NodeInternals) {
   let maxLevel = -1;
 
   const levelLookup = edges.reduce<Record<string, Edge[]>>((tree, edge) => {
-    const z = edge.zIndex || Math.max(nodeInternals.get(edge.source)?.z || 0, nodeInternals.get(edge.target)?.z || 0);
+    const z = isNumeric(edge.zIndex)
+      ? edge.zIndex
+      : Math.max(nodeInternals.get(edge.source)?.z || 0, nodeInternals.get(edge.target)?.z || 0);
     if (tree[z]) {
       tree[z].push(edge);
     } else {