diff --git a/src/resolver.js b/src/resolver.js
index cfd763b..29a96cd 100644
--- a/src/resolver.js
+++ b/src/resolver.js
@@ -12,6 +12,9 @@ export async function resolve(...paths) {
     // seems to be an URL, fetch it
     const resource = last;
     const response = await fetch(resource);
+    if (response.status >= 400) {
+      throw new Error('Not Found');
+    }
     const contentType = response.headers.get('Content-Type');
     if (!contentType || !contentType.startsWith('text')) {
       return await response.buffer();
diff --git a/src/transforms/template-data.js b/src/transforms/template-data.js
index b191b55..b42e775 100644
--- a/src/transforms/template-data.js
+++ b/src/transforms/template-data.js
@@ -88,10 +88,12 @@ export function template(str) {
  */
 export async function handleTemplateFile(config, data, inputFile) {
   const content = await (config.resolve || resolve)(config.dir.input, inputFile);
+  if (typeof content === "undefined") {
+    throw new Error('Not Found');
+  }
   if (content === null) {
     return null;
-  } 
-
+  }
   const parsed = path.parse(inputFile);
   const ext = parsed.ext?.slice(1);
   if (! config.extensions.has(ext)) {
@@ -120,7 +122,11 @@ export async function handleTemplateFile(config, data, inputFile) {
     const layoutFilePath = path.normalize(path.join(config.dir.layouts, fileData.layout));
     const l = await handleTemplateFile(config, 
       {...fileData, content: fileContent, layout: null}, layoutFilePath);
-    fileContent = l.content;
+    if (l) {
+      fileContent = l.content;;
+    } else {
+      throw new Error('Layout not found:' + layoutFilePath);
+    }
   }
 
   return {content: fileContent, filename: outputFile};
diff --git a/tests/resolver.test.js b/tests/resolver.test.js
index f72faa9..aa47b55 100644
--- a/tests/resolver.test.js
+++ b/tests/resolver.test.js
@@ -31,6 +31,7 @@ describe('resolve', () => {
       headers.set('Content-Type', 'text/css');
       
       return ({
+        status: 200,
         headers,
         async text() {return ':where(html){}'}
       })
@@ -43,4 +44,22 @@ describe('resolve', () => {
     globalThis.fetch = originalFetch;
   });
 
+  it('should not fetch stuff from the internet when the status code is an error', () => {
+    const originalFetch = globalThis.fetch;
+    globalThis.fetch = mock.fn(async () => {
+      const headers = new Map();
+      headers.set('Content-Type', 'text/html');
+      return ({
+        status: 404,
+        headers,
+        async text() {return 'Not Found'}
+      })
+    });
+
+    assert.rejects(async () => {
+      await resolve(config.dir.input, 'https://not-found.io/404.html');
+    });
+    globalThis.fetch = originalFetch;
+  });
+  
 });
diff --git a/tests/transforms/template-data.test.js b/tests/transforms/template-data.test.js
index f97c8fe..8efee55 100644
--- a/tests/transforms/template-data.test.js
+++ b/tests/transforms/template-data.test.js
@@ -21,11 +21,7 @@ const TEST_DATA = {
   }
 }
 
-const TEST_MD = `---
-layout: base.html
-author: Lea Rosema
----
-# {{ title }}
+const TEST_MD = `# {{ title }}
 
 An article by {{ author }}
 `
@@ -112,13 +108,72 @@ describe('template function', () => {
   });
 });
 
-describe('handleTemplateFile function', () => {
+describe('handleTemplateFile function', {only: true}, () => {
+
+  const withFrontmatter = (str, data) => `---json\n${JSON.stringify(data)}\n---\n${str}`
+
+  it('should work with basic html files without specifying a layout', async () => {
+    const config = new SissiConfig();
+    config.addExtension(md);
+
+    const vFS = new Map();
+    vFS.set('index.html', '<h1>{{ title }}</h1>');
+
+    config.resolve = (...paths) => {
+      const resource = path.normalize(path.join(...paths));
+      return vFS.get(resource);
+    }
+
+    const result = await handleTemplateFile(config, {title: 'Lea was here'}, 'index.html');
+
+    assert.equal(result.filename, 'public/index.html');
+    assert.equal(result.content, '<h1>Lea was here</h1>')
+  });
+
+  it('should work with basic html files with specifying a layout', async () => {
+    const config = new SissiConfig();
+    config.addExtension(md);
+
+    const vFS = new Map();
+    vFS.set('index.html', withFrontmatter('<h1>{{ title }}</h1>', {layout: 'base.html'}));
+    vFS.set('_layouts/base.html', '<body>{{ content }}</body>')
+
+    config.resolve = (...paths) => {
+      const resource = path.normalize(path.join(...paths));
+      return vFS.get(resource);
+    }
+
+    const result = await handleTemplateFile(config, {title: 'Lea was here'}, 'index.html');
+
+    assert.equal(result.filename, 'public/index.html');
+    assert.equal(result.content, '<body><h1>Lea was here</h1></body>');
+  });
+
   it('should work with the default markdown plugin', async () => {
     const config = new SissiConfig();
     config.addExtension(md);
 
     const vFS = new Map();
-    vFS.set('index.md', TEST_MD);
+    vFS.set('index.md', withFrontmatter(TEST_MD, {'layout': 'base.html', author: 'Lea Rosema'}));
+    vFS.set('_layouts/base.html', '<body>{{ content }}</body>');  
+
+    config.resolve = (...paths) => {
+      const resource = path.normalize(path.join(...paths));
+      return vFS.get(resource);
+    }
+
+    const result = await handleTemplateFile(config, {title: 'Lea was here'}, 'index.md');
+
+    assert.equal(result.filename, 'public/index.html');
+    assert.equal(result.content, '<body><h1>Lea was here</h1>\n\n<p>An article by Lea Rosema</p>\n</body>')
+  });
+
+  it('should work with the default markdown plugin.', async () => {
+    const config = new SissiConfig();
+    config.addExtension(md);
+
+    const vFS = new Map();
+    vFS.set('index.md', withFrontmatter(TEST_MD, {'layout': 'base.html', author: 'Lea Rosema'}));
     vFS.set('_layouts/base.html', '<body>{{ content }}</body>');  
 
     config.resolve = (...paths) => {
@@ -131,4 +186,43 @@ describe('handleTemplateFile function', () => {
     assert.equal(result.filename, 'public/index.html');
     assert.equal(result.content, '<body><h1>Lea was here</h1>\n\n<p>An article by Lea Rosema</p>\n</body>')
   });
+
+  it('should throw an error when a non-existant file is specified', async () => {
+    const config = new SissiConfig();
+    config.addExtension(md);
+
+    const vFS = new Map();
+    vFS.set('index.md', withFrontmatter(TEST_MD, {'layout': 'notfound.html', author: 'Lea Rosema'}));
+
+    config.resolve = (...paths) => {
+      const resource = path.normalize(path.join(...paths));
+      if (vFS.has(resource)) {
+        return vFS.get(resource);
+      }
+    }
+
+    assert.rejects(async () => {
+      await handleTemplateFile(config, {title: 'Lea was here'}, 'something-completely-different.md');
+    });
+  });
+
+  it('should throw an error when a non-existant file is specified as layout', {only: true}, async () => {
+    const config = new SissiConfig();
+    config.addExtension(md);
+
+    const vFS = new Map();
+    vFS.set('index.md', withFrontmatter(TEST_MD, {'layout': 'notfound.html', author: 'Lea Rosema'}));
+
+    config.resolve = (...paths) => {
+      const resource = path.normalize(path.join(...paths));
+      if (vFS.has(resource)) {
+        return vFS.get(resource);
+      }
+    }
+
+    assert.rejects(async () => {
+      await handleTemplateFile(config, {title: 'Lea was here'}, 'index.md');
+    });
+  });
+
 });