diff --git a/__mocks__/dns.js b/__mocks__/dns.js
index 96cf4e8..ad7a5a6 100644
--- a/__mocks__/dns.js
+++ b/__mocks__/dns.js
@@ -21,4 +21,8 @@ export function lookup(hostname, options, callback) {
   ) {
     callback(undefined, { address: '1.1.1.1', family: 4 })
   }
+
+  // Really make sure that all test cases - at least, the ones that resolve an actual hostname -
+  // have a corresponding DNS mock as well (on top of the HTTP mock).
+  callback(new Error('Could not resolve host'))
 }
diff --git a/index.js b/index.js
index 2512245..2375ab7 100644
--- a/index.js
+++ b/index.js
@@ -29,13 +29,34 @@ const protect = async options => {
   if (!ALLOWED_PROTOCOLS.includes(options.url.protocol))
     throw new Error('Invalid protocol!')
 
-  // Another layer of protection against SSRF - ensure we're not hitting internal services
-  const { address } = await lookup(options.url.hostname)
+  // Check if the hostname is an IP address - we don't need to "lookup" IP addresses!
+  let IP
+  const { hostname } = options.url
+
+  if (ip.IPv4.isIPv4(hostname)) {
+    IP = hostname
+  } else if (
+    // Per https://url.spec.whatwg.org/#host-parsing,
+    // if the hostname starts with a [, we need to check if it ends with a ], and is an IPv6.
+    hostname.startsWith('[') &&
+    hostname.endsWith(']') &&
+    ip.IPv6.isIPv6(hostname.slice(1, -1)) // strip the first and last characters - the brackets
+  ) {
+    IP = hostname.slice(1, -1)
+  } else {
+    // A regular hostname - we need to do a DNS lookup to get the IP address
+    const { address } = await lookup(hostname)
+    IP = address
+  }
+
+  // Another layer of protection against SSRF - ensure we're not hitting internal services.
   // Try to match "reserved" IP ranges: https://en.wikipedia.org/wiki/Reserved_IP_addresses
   // https://cheatsheetseries.owasp.org/cheatsheets/Server_Side_Request_Forgery_Prevention_Cheat_Sheet.html#case-2-application-can-send-requests-to-any-external-ip-address-or-domain-name
   // The function returns 'unicast' or the name of the reserved IP range, should it match any.
   // This in effect blocks all private IP Range: https://git.io/JWy3u, https://git.io/JWy3b
-  if (ip.parse(address).range() !== 'unicast')
+  // We use ip.process() here to deal with potentially IPv4-mapped IPv6 addresses (which will show up as "ipv4mapped"
+  // and not the whatever range the actual IPv4 address actually belongs to).
+  if (ip.process(IP).range() !== 'unicast')
     throw new Error('The IP of the domain is reserved!')
 }
 
diff --git a/index.test.js b/index.test.js
index a7239da..440b1e2 100644
--- a/index.test.js
+++ b/index.test.js
@@ -33,4 +33,53 @@ describe('got-ssrf', () => {
       )
     ).rejects.toThrow('The IP of the domain is reserved!')
   })
+
+  // NOTE: for IP address tests, any valid IP address will be processed directly in the code,
+  // without the need for a DNS lookup (after all, you do a DNS lookup to get the IP address).
+  // Therefore, we do not need DNS mocks (__mocks__/dns.js) for the tests below.
+
+  it('handles IPv4 addresses', async () => {
+    // A private IPv4 address
+    await expect(gotSsrf('http://192.168.0.1')).rejects.toThrow(
+      'The IP of the domain is reserved!'
+    )
+
+    // A public IPv4 address
+    nock('http://1.1.1.1').get('/').reply(200)
+    await gotSsrf('http://1.1.1.1')
+  })
+
+  it('handles IPv6 addresses', async () => {
+    // This is 127.0.0.1 mapped to IPv6
+    await expect(gotSsrf('http://[::ffff:7f00:1]:1338/hello')).rejects.toThrow(
+      'The IP of the domain is reserved!'
+    )
+
+    // A public IPv4 address (1.1.1.1) mapped to IPv6
+    nock('http://[::ffff:101:101]').get('/').reply(200)
+    await gotSsrf('http://[::ffff:101:101]')
+
+    // A public IPv6 address
+    nock('http://[2606:2800:220:1:248:1893:25c8:1946]').get('/').reply(200)
+    await gotSsrf('http://[2606:2800:220:1:248:1893:25c8:1946]')
+
+    // A private IPv6 address
+    await expect(gotSsrf('http://[fe80::ffff:ffff:ffff:ffff]')).rejects.toThrow(
+      'The IP of the domain is reserved!'
+    )
+  })
+
+  it('handles hostnames with brackets in it', async () => {
+    await expect(gotSsrf('http://[hostname1.com')).rejects.toThrow(
+      'Invalid URL'
+    )
+
+    await expect(gotSsrf('http://[hostnam]e2.com')).rejects.toThrow(
+      'Invalid URL'
+    )
+
+    await expect(
+      gotSsrf('http://[2606:2800:220:1:248:1893:25c8:g]')
+    ).rejects.toThrow('Invalid URL')
+  })
 })