diff --git a/app/soapbox/normalizers/__tests__/attachment-test.js b/app/soapbox/normalizers/__tests__/attachment-test.js
new file mode 100644
index 000000000..ecf3813e7
--- /dev/null
+++ b/app/soapbox/normalizers/__tests__/attachment-test.js
@@ -0,0 +1,21 @@
+import { Record as ImmutableRecord, fromJS } from 'immutable';
+
+import { normalizeAttachment } from '../attachment';
+
+describe('normalizeAttachment()', () => {
+  it('adds base fields', () => {
+    const attachment = fromJS({});
+    const result = normalizeAttachment(attachment);
+
+    expect(ImmutableRecord.isRecord(result)).toBe(true);
+    expect(result.type).toEqual('unknown');
+    expect(result.url).toEqual('');
+  });
+
+  it('infers preview_url from url', () => {
+    const attachment = fromJS({ url: 'https://site.fedi/123.png' });
+    const result = normalizeAttachment(attachment);
+
+    expect(result.preview_url).toEqual('https://site.fedi/123.png');
+  });
+});
diff --git a/app/soapbox/normalizers/attachment.ts b/app/soapbox/normalizers/attachment.ts
new file mode 100644
index 000000000..9599fc1ce
--- /dev/null
+++ b/app/soapbox/normalizers/attachment.ts
@@ -0,0 +1,45 @@
+/**
+ * Attachment normalizer:
+ * Converts API attachments into our internal format.
+ * @see {@link https://docs.joinmastodon.org/entities/attachment/}
+ */
+import {
+  Map as ImmutableMap,
+  Record as ImmutableRecord,
+} from 'immutable';
+
+import { mergeDefined } from 'soapbox/utils/normalizers';
+
+// https://docs.joinmastodon.org/entities/attachment/
+const AttachmentRecord = ImmutableRecord({
+  blurhash: undefined,
+  description: '',
+  id: '',
+  meta: ImmutableMap(),
+  pleroma: ImmutableMap(),
+  preview_url: '',
+  remote_url: null,
+  type: 'unknown',
+  url: '',
+
+  // Internal fields
+  // TODO: Remove these? They're set in selectors/index.js
+  account: null,
+  status: null,
+});
+
+// Ensure attachments have required fields
+export const normalizeAttachment = (attachment: ImmutableMap<string, any>) => {
+  const url = [
+    attachment.get('url'),
+    attachment.get('preview_url'),
+    attachment.get('remote_url'),
+  ].find(url => url) || '';
+
+  const base = ImmutableMap({
+    url,
+    preview_url: url,
+  });
+
+  return AttachmentRecord(attachment.mergeWith(mergeDefined, base));
+};
diff --git a/app/soapbox/normalizers/status.ts b/app/soapbox/normalizers/status.ts
index 91c52cfa3..4cbf83e5b 100644
--- a/app/soapbox/normalizers/status.ts
+++ b/app/soapbox/normalizers/status.ts
@@ -9,11 +9,11 @@ import {
   Record as ImmutableRecord,
 } from 'immutable';
 
+import { normalizeAttachment } from 'soapbox/normalizers/attachment';
 import { normalizeEmoji } from 'soapbox/normalizers/emoji';
 import { normalizeMention } from 'soapbox/normalizers/mention';
 import { normalizePoll } from 'soapbox/normalizers/poll';
 import { IStatus } from 'soapbox/types';
-import { mergeDefined } from 'soapbox/utils/normalizers';
 
 // https://docs.joinmastodon.org/entities/status/
 const StatusRecord = ImmutableRecord({
@@ -55,39 +55,6 @@ const StatusRecord = ImmutableRecord({
   spoilerHtml: '',
 });
 
-// https://docs.joinmastodon.org/entities/attachment/
-const AttachmentRecord = ImmutableRecord({
-  blurhash: undefined,
-  description: '',
-  id: '',
-  meta: ImmutableMap(),
-  pleroma: ImmutableMap(),
-  preview_url: '',
-  remote_url: null,
-  type: 'unknown',
-  url: '',
-
-  // Internal fields
-  account: null,
-  status: null,
-});
-
-// Ensure attachments have required fields
-const normalizeAttachment = (attachment: ImmutableMap<string, any>) => {
-  const url = [
-    attachment.get('url'),
-    attachment.get('preview_url'),
-    attachment.get('remote_url'),
-  ].find(url => url) || '';
-
-  const base = ImmutableMap({
-    url,
-    preview_url: url,
-  });
-
-  return AttachmentRecord(attachment.mergeWith(mergeDefined, base));
-};
-
 const normalizeAttachments = (status: ImmutableMap<string, any>) => {
   return status.update('media_attachments', ImmutableList(), attachments => {
     return attachments.map(normalizeAttachment);