diff --git a/scripts/serverPmTileExtracts.ts b/scripts/serverPmTileExtracts.ts
index e63ac2cce..09757ccc3 100644
--- a/scripts/serverPmTileExtracts.ts
+++ b/scripts/serverPmTileExtracts.ts
@@ -37,8 +37,8 @@ class ServerPmTileExtracts extends Script {
                                    body: string,
                                    res: ServerResponse) => {
                         const [z,x,y] = path.split(".")[0].split("/").map(x => Number(x))
-                        if(z in zoomlevels){
-                            throw "Invalid zoomlevel, must be one of "+Array.from(Object.keys(zoomlevels)).join(", ")
+                        if(!(z in zoomlevels)){
+                            throw `Invalid zoomlevel ${z} (x: ${x}, y: ${y}, must be one of ${Array.from(Object.keys(zoomlevels)).join(", ")}`
                         }
 
                         const targetFile = generator.getFilename(z, x, y)