diff --git a/backend/tests/Squidex.Data.Tests/EntityFramework/Migrations/PostgresMigrationTests.cs b/backend/tests/Squidex.Data.Tests/EntityFramework/Migrations/PostgresMigrationTests.cs
index d7dd7a589..6e7a7dd70 100644
--- a/backend/tests/Squidex.Data.Tests/EntityFramework/Migrations/PostgresMigrationTests.cs
+++ b/backend/tests/Squidex.Data.Tests/EntityFramework/Migrations/PostgresMigrationTests.cs
@@ -8,7 +8,9 @@
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
 using Squidex.Domain.Apps.Core.TestHelpers;
+using Squidex.Infrastructure;
 using Squidex.Infrastructure.Migrations;
+using Squidex.Infrastructure.Queries;
 using Squidex.Providers.Postgres;
 using Squidex.Providers.Postgres.App;
 using Testcontainers.PostgreSql;
@@ -19,7 +21,7 @@ namespace Squidex.EntityFramework.Migrations;
 public class PostgresMigrationTests : IAsyncLifetime
 {
     private readonly PostgreSqlContainer postgreSql =
-        new PostgreSqlBuilder("postgis/postgis")
+        new PostgreSqlBuilder("imresamu/postgis:16-3.4")
             .Build();
 
     public async ValueTask InitializeAsync()
@@ -59,4 +61,79 @@ public class PostgresMigrationTests : IAsyncLifetime
         var migrations = await dbContext.Database.GetAppliedMigrationsAsync();
         Assert.NotEmpty(migrations);
     }
+
+    [Fact]
+    public async Task Should_migrate_idempotent_and_functions_callable()
+    {
+        var services =
+            new ServiceCollection()
+                .AddDbContextFactory<PostgresAppDbContext>(b =>
+                {
+                    b.UseNpgsql(postgreSql.GetConnectionString(), options =>
+                    {
+                        options.UseNetTopologySuite();
+                    });
+                })
+                .AddSingleton<ConnectionStringParser, PostgresConnectionStringParser>()
+                .AddSingleton(TestUtils.DefaultSerializer)
+                .AddSingleton<DatabaseMigrator<PostgresAppDbContext>>()
+                .BuildServiceProvider();
+
+        var databaseMigrator = services.GetRequiredService<DatabaseMigrator<PostgresAppDbContext>>();
+        var databaseFactory = services.GetRequiredService<IDbContextFactory<PostgresAppDbContext>>();
+
+        // Run migrations twice to verify idempotency.
+        await databaseMigrator.InitializeAsync(default);
+        await databaseMigrator.InitializeAsync(default);
+
+        // Verify the jsonb_exists function was created and is callable.
+        // Note: {{ and }} are escaped braces for ExecuteSqlRawAsync's string.Format-style parser.
+        await using var dbContext = await databaseFactory.CreateDbContextAsync();
+        var result = await dbContext.Database.ExecuteSqlRawAsync(
+            "SELECT jsonb_exists('{{\"a\":1}}'::jsonb)");
+        Assert.Equal(-1, result);
+    }
+
+    [Fact]
+    public async Task Should_migrate_when_functions_already_exist()
+    {
+        var services =
+            new ServiceCollection()
+                .AddDbContextFactory<PostgresAppDbContext>(b =>
+                {
+                    b.UseNpgsql(postgreSql.GetConnectionString(), options =>
+                    {
+                        options.UseNetTopologySuite();
+                    });
+                })
+                .AddSingleton<ConnectionStringParser, PostgresConnectionStringParser>()
+                .AddSingleton(TestUtils.DefaultSerializer)
+                .AddSingleton<DatabaseMigrator<PostgresAppDbContext>>()
+                .BuildServiceProvider();
+
+        var databaseMigrator = services.GetRequiredService<DatabaseMigrator<PostgresAppDbContext>>();
+        var databaseFactory = services.GetRequiredService<IDbContextFactory<PostgresAppDbContext>>();
+
+        // Simulate a pre-migration database: apply all migrations up to (but not including)
+        // AddJsonFunctions, then create the functions via the old SqlDialectInitializer path.
+        await using (var dbContext = await databaseFactory.CreateDbContextAsync())
+        {
+            await dbContext.Database.MigrateAsync("20260323155026_MigrateToNet10");
+
+            if (dbContext is IDbContextWithDialect withDialect)
+            {
+                await withDialect.Dialect.InitializeAsync(dbContext, default);
+            }
+        }
+
+        // Run the full migration — should apply AddJsonFunctions on top of already-existing functions.
+        await databaseMigrator.InitializeAsync(default);
+
+        // Verify the functions are still callable after migration.
+        // Note: {{ and }} are escaped braces for ExecuteSqlRawAsync's string.Format-style parser.
+        await using var verifyContext = await databaseFactory.CreateDbContextAsync();
+        var result = await verifyContext.Database.ExecuteSqlRawAsync(
+            "SELECT jsonb_exists('{{\"a\":1}}'::jsonb)");
+        Assert.Equal(-1, result);
+    }
 }
diff --git a/backend/tests/Squidex.Data.Tests/EntityFramework/TestHelpers/PostgresFixture.cs b/backend/tests/Squidex.Data.Tests/EntityFramework/TestHelpers/PostgresFixture.cs
index 4f613fd46..db5d7e09c 100644
--- a/backend/tests/Squidex.Data.Tests/EntityFramework/TestHelpers/PostgresFixture.cs
+++ b/backend/tests/Squidex.Data.Tests/EntityFramework/TestHelpers/PostgresFixture.cs
@@ -23,7 +23,7 @@ namespace Squidex.EntityFramework.TestHelpers;
 public class PostgresFixture(string? reuseId) : IAsyncLifetime, ISqlContentFixture<TestDbContextPostgres, PostgresContentDbContext>
 {
     private readonly PostgreSqlContainer postgreSql =
-        new PostgreSqlBuilder("postgis/postgis")
+        new PostgreSqlBuilder("imresamu/postgis:16-3.4")
             .WithReuse(true)
             .WithLabel("reuse-id", reuseId)
             .Build();