diff --git a/lib/OpenLayers/Layer/TileCache.js b/lib/OpenLayers/Layer/TileCache.js
index 7058c5da03..ddf6a7c714 100644
--- a/lib/OpenLayers/Layer/TileCache.js
+++ b/lib/OpenLayers/Layer/TileCache.js
@@ -105,7 +105,9 @@ OpenLayers.Layer.TileCache = OpenLayers.Class(OpenLayers.Layer.Grid, {
         var size = this.tileSize;
         var tileX = Math.round((bounds.left - bbox.left) / (res * size.w));
         var tileY = Math.round((bounds.bottom - bbox.bottom) / (res * size.h));
-        var tileZ = this.serverResolutions != null ? this.serverResolutions.indexOf(res) : this.map.getZoom();
+        var tileZ = this.serverResolutions != null ?
+            OpenLayers.Util.indexOf(this.serverResolutions, res) :
+            this.map.getZoom();
         /**
          * Zero-pad a positive integer.
          * number - {Int} 
diff --git a/tests/Layer/TileCache.html b/tests/Layer/TileCache.html
index 216979e741..d24a44acc9 100644
--- a/tests/Layer/TileCache.html
+++ b/tests/Layer/TileCache.html
@@ -159,7 +159,8 @@
         layer.serverResolutions = [14,13,12,11,10];
         tileurl = layer.getURL(new OpenLayers.Bounds(0,0,0,0));
         level = parseInt(tileurl.split('/')[2]);
-        t.eq(layer.serverResolutions.indexOf(map.getResolution()), level, "Tile zoom level is correct with serverResolutions");
+        var gotLevel = OpenLayers.Util.indexOf(layer.serverResolutions, map.getResolution());
+        t.eq(gotLevel, level, "Tile zoom level is correct with serverResolutions");
         
         map.destroy();
     }