diff --git a/README.md b/README.md
index 07a096f..c82ea0f 100644
--- a/README.md
+++ b/README.md
@@ -47,7 +47,7 @@ mysql> FLUSH PRIVILEGES;
 
 Populate the database using knex, which should add tables automatically.<br>
 ```
-knex --knexfile src/knexfile.ts migrate:latest
+make knex-migrate
 ```
 
 This should populate your database with the required tables.
diff --git a/src/db-types.ts b/src/db-types.ts
index a5925a3..384d1c6 100644
--- a/src/db-types.ts
+++ b/src/db-types.ts
@@ -31,6 +31,7 @@ export type EntriesRecord = {
   billable: number;
   created_at: Date;
   modified_at: Date;
+  version: number;
 }
 
 export type PeopleRecord = {
diff --git a/src/entry/controller/item.ts b/src/entry/controller/item.ts
index 64f3ab6..253fdb6 100644
--- a/src/entry/controller/item.ts
+++ b/src/entry/controller/item.ts
@@ -18,13 +18,13 @@ class Entry extends Controller {
     const person = await personService.findById(
       +ctx.params.personId,
     );
-
-    ctx.response.body = hal.item(
-      await entryService.findById(
-        person,
-        +ctx.params.entryId,
-      )
+    const entry = await entryService.findById(
+      person,
+      +ctx.params.entryId,
     );
+
+    ctx.response.body = hal.item(entry);
+    ctx.response.headers.set('ETag', '"' + entry.version + '"');
   }
 
   async put(ctx: Context) {
diff --git a/src/entry/formats/hal.ts b/src/entry/formats/hal.ts
index ed9bfec..64ec874 100644
--- a/src/entry/formats/hal.ts
+++ b/src/entry/formats/hal.ts
@@ -50,6 +50,9 @@ export function item(entry: Entry) {
         href: entry.person.href
       }
     },
+    _headers: {
+      ETag: '"' + entry.version + '"',
+    },
     description: entry.description,
     date: entry.date,
     minutes: entry.minutes,
diff --git a/src/entry/service.ts b/src/entry/service.ts
index 84f642b..d59d42d 100644
--- a/src/entry/service.ts
+++ b/src/entry/service.ts
@@ -135,13 +135,15 @@ export async function create(entry: NewEntry): Promise<Entry> {
     description: entry.description,
     billable: entry.billable,
     created_at: new Date(),
-    modified_at: new Date()
+    modified_at: new Date(),
+    version: 1,
   });
 
   return {
     ...entry,
     id: result[0],
     href: `/person/${entry.person.id}/entry/${result[0]}`,
+    version: 1,
     createdAt: new Date(),
     modifiedAt: new Date()
   };
@@ -150,14 +152,17 @@ export async function create(entry: NewEntry): Promise<Entry> {
 
 export async function update(entry: Entry): Promise<void> {
 
-  await knex('entries').update({
-    project_id: entry.project.id,
-    date: entry.date,
-    minutes: entry.minutes,
-    description: entry.description,
-    billable: entry.billable,
-    modified_at: new Date()
-  }).where({id: entry.id});
+  await knex('entries')
+    .update({
+      project_id: entry.project.id,
+      date: entry.date,
+      minutes: entry.minutes,
+      description: entry.description,
+      billable: entry.billable,
+      modified_at: new Date(),
+    })
+    .increment('version', 1)
+    .where({id: entry.id});
 
 }
 
@@ -180,7 +185,8 @@ function mapRecord(input: EntriesRecord, project: Project, person: Person): Entr
     description: input.description,
     billable: !!input.billable,
     createdAt: input.created_at,
-    modifiedAt: input.modified_at
+    modifiedAt: input.modified_at,
+    version: input.version,
   };
 
 }
diff --git a/src/migrations/20221027052445_entry_version.ts b/src/migrations/20221027052445_entry_version.ts
new file mode 100644
index 0000000..859068f
--- /dev/null
+++ b/src/migrations/20221027052445_entry_version.ts
@@ -0,0 +1,24 @@
+import { Knex } from 'knex';
+
+
+export async function up(knex: Knex): Promise<void> {
+
+  await knex.schema.alterTable('entries', table => {
+
+    table.integer('version').unsigned().notNullable().defaultTo(1);
+
+  });
+
+}
+
+
+export async function down(knex: Knex): Promise<void> {
+
+  await knex.schema.alterTable('entries', table => {
+
+    table.dropColumn('version');
+
+  });
+
+}
+
diff --git a/src/types.ts b/src/types.ts
index cfc0fd7..ea4650a 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -50,8 +50,9 @@ export type Entry = {
 
   modifiedAt: Date;
   createdAt: Date;
+  version: number;
 
 }
 
 export type NewEntry =
-  Omit<Entry, 'id' | 'href' | 'modifiedAt' | 'createdAt'>;
+  Omit<Entry, 'id' | 'href' | 'modifiedAt' | 'createdAt' | 'version'>;