diff --git a/packages/backend-app-api/src/lib/http/config.test.ts b/packages/backend-app-api/src/lib/http/config.test.ts
new file mode 100644
index 0000000000..3ab5eda5e9
--- /dev/null
+++ b/packages/backend-app-api/src/lib/http/config.test.ts
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2020 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { ConfigReader } from '@backstage/config';
+import { readHttpServerOptions } from './config';
+
+describe('readHttpServerOptions', () => {
+  it.each([
+    [{}, { listen: { host: '', port: 7007 } }],
+    [{ listen: ':80' }, { listen: { host: '', port: 80 } }],
+    [{ listen: '80' }, { listen: { host: '', port: 80 } }],
+    [{ listen: '1.2.3.4:80' }, { listen: { host: '1.2.3.4', port: 80 } }],
+    [{ listen: { host: '' } }, { listen: { host: '', port: 7007 } }],
+    [
+      { listen: { host: '0.0.0.0' } },
+      { listen: { host: '0.0.0.0', port: 7007 } },
+    ],
+    [
+      { listen: { host: '0.0.0.0', port: '80' } },
+      { listen: { host: '0.0.0.0', port: 80 } },
+    ],
+    [{ listen: { port: '80' } }, { listen: { host: '', port: 80 } }],
+    [{ listen: { port: 80 } }, { listen: { host: '', port: 80 } }],
+    [{ listen: { port: 80 } }, { listen: { host: '', port: 80 } }],
+    [
+      { baseUrl: 'http://example.com:8080', https: true },
+      {
+        listen: { host: '', port: 7007 },
+        https: { certificate: { type: 'generated', hostname: 'example.com' } },
+      },
+    ],
+    [
+      { https: { certificate: { cert: 'my-cert', key: 'my-key' } } },
+      {
+        listen: { host: '', port: 7007 },
+        https: {
+          certificate: { type: 'plain', cert: 'my-cert', key: 'my-key' },
+        },
+      },
+    ],
+  ])('should read http server options %#', (input, output) => {
+    expect(readHttpServerOptions(new ConfigReader(input))).toEqual(output);
+  });
+
+  it.each([
+    [
+      { listen: { port: 'not-a-number' } },
+      "Unable to convert config value for key 'listen.port' in 'mock-config' to a number",
+    ],
+    [
+      { listen: { port: {} } },
+      "Invalid type in config for key 'listen.port' in 'mock-config', got object, wanted number",
+    ],
+    [
+      { listen: { host: false } },
+      "Invalid type in config for key 'listen.host' in 'mock-config', got boolean, wanted string",
+    ],
+    [{ https: {} }, "Missing required config value at 'https.certificate.cert"],
+    [
+      { https: { certificate: { cert: 'x' } } },
+      "Missing required config value at 'https.certificate.key",
+    ],
+  ])('should throw on bad options %#', (input, message) => {
+    expect(() => readHttpServerOptions(new ConfigReader(input))).toThrow(
+      message,
+    );
+  });
+});
diff --git a/packages/backend-app-api/src/lib/http/config.ts b/packages/backend-app-api/src/lib/http/config.ts
index 933bab42a0..3c5acf0ffd 100644
--- a/packages/backend-app-api/src/lib/http/config.ts
+++ b/packages/backend-app-api/src/lib/http/config.ts
@@ -42,9 +42,9 @@ export function readHttpServerOptions(config: Config): HttpServerOptions {
 }
 
 function readHttpListenOptions(config: Config): HttpServerOptions['listen'] {
-  const listen = config.get('listen');
+  const listen = config.getOptional('listen');
   if (typeof listen === 'string') {
-    const parts = listen.split(':');
+    const parts = String(listen).split(':');
     const port = parseInt(parts[parts.length - 1], 10);
     if (!isNaN(port)) {
       if (parts.length === 1) {
@@ -59,9 +59,16 @@ function readHttpListenOptions(config: Config): HttpServerOptions['listen'] {
     );
   }
 
+  // Workaround to allow empty string
+  const host = config.getOptional('listen.host') ?? DEFAULT_HOST;
+  if (typeof host !== 'string') {
+    config.getOptionalString('listen.host'); // will throw
+    throw new Error('unreachable');
+  }
+
   return {
     port: config.getOptionalNumber('listen.port') ?? DEFAULT_PORT,
-    host: config.getOptionalString('listen.host') ?? DEFAULT_HOST,
+    host,
   };
 }