diff --git a/app/build.gradle b/app/build.gradle
index b4435348..d973c8e4 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -91,7 +91,7 @@ play {
 }
 
 greendao {
-    schemaVersion 26
+    schemaVersion 27
     generateTests = true
 }
 
diff --git a/app/src/main/java/io/github/wulkanowy/data/db/dao/DbHelper.java b/app/src/main/java/io/github/wulkanowy/data/db/dao/DbHelper.java
index 07307e52..8aa9b1df 100644
--- a/app/src/main/java/io/github/wulkanowy/data/db/dao/DbHelper.java
+++ b/app/src/main/java/io/github/wulkanowy/data/db/dao/DbHelper.java
@@ -18,6 +18,7 @@ import io.github.wulkanowy.api.Vulcan;
 import io.github.wulkanowy.data.db.dao.entities.DaoMaster;
 import io.github.wulkanowy.data.db.dao.migrations.Migration23;
 import io.github.wulkanowy.data.db.dao.migrations.Migration26;
+import io.github.wulkanowy.data.db.dao.migrations.Migration27;
 import io.github.wulkanowy.data.db.shared.SharedPrefContract;
 import io.github.wulkanowy.di.annotations.ApplicationContext;
 import io.github.wulkanowy.di.annotations.DatabaseInfo;
@@ -76,6 +77,7 @@ public class DbHelper extends DaoMaster.OpenHelper {
         List<Migration> migrations = new ArrayList<>();
         migrations.add(new Migration23());
         migrations.add(new Migration26());
+        migrations.add(new Migration27());
 
         // Sorting just to be safe, in case other people add migrations in the wrong order.
         Comparator<Migration> migrationComparator = new Comparator<Migration>() {
diff --git a/app/src/main/java/io/github/wulkanowy/data/db/dao/entities/Exam.java b/app/src/main/java/io/github/wulkanowy/data/db/dao/entities/Exam.java
index 076846e1..543b6859 100644
--- a/app/src/main/java/io/github/wulkanowy/data/db/dao/entities/Exam.java
+++ b/app/src/main/java/io/github/wulkanowy/data/db/dao/entities/Exam.java
@@ -4,13 +4,15 @@ import org.greenrobot.greendao.DaoException;
 import org.greenrobot.greendao.annotation.Entity;
 import org.greenrobot.greendao.annotation.Generated;
 import org.greenrobot.greendao.annotation.Id;
+import org.greenrobot.greendao.annotation.Index;
 import org.greenrobot.greendao.annotation.Property;
 
 import java.io.Serializable;
 
 @Entity(
         nameInDb = "Exams",
-        active = true
+        active = true,
+        indexes = {@Index(value = "dayId,entryDate,subjectAndGroup,type,teacher", unique = true)}
 )
 
 public class Exam implements Serializable {
diff --git a/app/src/main/java/io/github/wulkanowy/data/db/dao/migrations/Migration27.java b/app/src/main/java/io/github/wulkanowy/data/db/dao/migrations/Migration27.java
new file mode 100644
index 00000000..5c8c82f1
--- /dev/null
+++ b/app/src/main/java/io/github/wulkanowy/data/db/dao/migrations/Migration27.java
@@ -0,0 +1,24 @@
+package io.github.wulkanowy.data.db.dao.migrations;
+
+import org.greenrobot.greendao.database.Database;
+
+import io.github.wulkanowy.api.Vulcan;
+import io.github.wulkanowy.data.db.dao.DbHelper;
+import io.github.wulkanowy.data.db.dao.entities.ExamDao;
+import io.github.wulkanowy.data.db.shared.SharedPrefContract;
+
+public class Migration27 implements DbHelper.Migration {
+
+    @Override
+    public Integer getVersion() {
+        return 27;
+    }
+
+    @Override
+    public void runMigration(Database db, SharedPrefContract sharedPref, Vulcan vulcan) throws Exception {
+        ExamDao.dropTable(db, true);
+        ExamDao.createTable(db, true);
+
+        db.execSQL("UPDATE Weeks SET exams_synced = 0");
+    }
+}