diff --git a/src/ol/render/canvas/hitdetect.js b/src/ol/render/canvas/hitdetect.js
index b3da3725ff..c907a736ed 100644
--- a/src/ol/render/canvas/hitdetect.js
+++ b/src/ol/render/canvas/hitdetect.js
@@ -114,7 +114,7 @@ export function createHitDetectionImageData(
           })
         );
       }
-      const zIndex = Number(style.getZIndex());
+      const zIndex = style.getZIndex() || 0;
       let byGeometryType = featuresByZIndex[zIndex];
       if (!byGeometryType) {
         byGeometryType = {};