diff --git a/js/adapters.ts b/js/adapters.ts
index c22e5eb..a6035fe 100644
--- a/js/adapters.ts
+++ b/js/adapters.ts
@@ -1,5 +1,5 @@
 declare const L: any;
-import { PMTiles, Source } from "./index";
+import { PMTiles, Source, TileType } from "./index";
 
 export const leafletRasterLayer = (source: PMTiles, options: any) => {
   const cls = L.GridLayer.extend({
@@ -51,6 +51,28 @@ export const leafletRasterLayer = (source: PMTiles, options: any) => {
   return new cls(options);
 };
 
+// copied from MapLibre /util/ajax.ts
+type RequestParameters = {
+  url: string;
+  headers?: any;
+  method?: "GET" | "POST" | "PUT";
+  body?: string;
+  type?: "string" | "json" | "arrayBuffer";
+  credentials?: "same-origin" | "include";
+  collectResourceTiming?: boolean;
+};
+
+type ResponseCallback = (
+  error?: Error | null,
+  data?: any | null,
+  cacheControl?: string | null,
+  expires?: string | null
+) => void;
+
+type Cancelable = {
+  cancel: () => void;
+};
+
 export class Protocol {
   tiles: Map<string, PMTiles>;
 
@@ -66,7 +88,10 @@ export class Protocol {
     return this.tiles.get(url);
   }
 
-  tile = (params: any, callback: any) => {
+  tile = (
+    params: RequestParameters,
+    callback: ResponseCallback
+  ): Cancelable => {
     if (params.type == "json") {
       const pmtiles_url = params.url.substr(10);
       let instance = this.tiles.get(pmtiles_url);
@@ -75,6 +100,8 @@ export class Protocol {
         this.tiles.set(pmtiles_url, instance);
       }
 
+      // TODO: create vector_layers if present to return valid TileJSON
+
       instance.getHeader().then((h) => {
         const tilejson = {
           tiles: [params.url + "/{z}/{x}/{y}"],
@@ -83,13 +110,18 @@ export class Protocol {
         };
         callback(null, tilejson, null, null);
       });
-
       return {
         cancel: () => {},
       };
     } else {
       const re = new RegExp(/pmtiles:\/\/(.+)\/(\d+)\/(\d+)\/(\d+)/);
       const result = params.url.match(re);
+      if (!result) {
+        throw new Error("Invalid PMTiles protocol URL");
+        return {
+          cancel: () => {},
+        };
+      }
       const pmtiles_url = result[1];
 
       let instance = this.tiles.get(pmtiles_url);
@@ -107,25 +139,31 @@ export class Protocol {
         controller.abort();
       };
 
-      instance
-        .getZxy(+z, +x, +y, signal)
-        .then((resp) => {
-          if (resp) {
-            callback(
-              null,
-              new Uint8Array(resp.data),
-              resp.cacheControl,
-              resp.expires
-            );
-          } else {
-            callback(null, new Uint8Array(), null, null);
-          }
-        })
-        .catch((e) => {
-          if (e.name !== "AbortError") {
-            throw e;
-          }
-        });
+      instance.getHeader().then((header) => {
+        instance!
+          .getZxy(+z, +x, +y, signal)
+          .then((resp) => {
+            if (resp) {
+              callback(
+                null,
+                new Uint8Array(resp.data),
+                resp.cacheControl,
+                resp.expires
+              );
+            } else {
+              if (header.tileType == TileType.Mvt) {
+                callback(null, new Uint8Array(), null, null);
+              } else {
+                callback(null, null, null, null);
+              }
+            }
+          })
+          .catch((e) => {
+            if ((e as Error).name !== "AbortError") {
+              throw e;
+            }
+          });
+      });
       return {
         cancel: cancel,
       };