diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.Host.IntegrationTests/ServerHistorianOptionsValidatorTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.Host.IntegrationTests/ServerHistorianOptionsValidatorTests.cs
index d6447d73..00945b11 100644
--- a/tests/Server/ZB.MOM.WW.OtOpcUa.Host.IntegrationTests/ServerHistorianOptionsValidatorTests.cs
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.Host.IntegrationTests/ServerHistorianOptionsValidatorTests.cs
@@ -339,4 +339,40 @@ public sealed class ServerHistorianOptionsValidatorTests
     [Fact]
     public void SqlServer_backend_not_consumed_passes_without_connection_string() =>
         SqlSut(null).Validate(null, new ServerHistorianOptions { Backend = "SqlServer" }).Failed.ShouldBeFalse();
+
+    private static IConfiguration BadSchemaConfig(bool alarmHistorianEnabled) =>
+        new ConfigurationBuilder().AddInMemoryCollection(new Dictionary<string, string?>
+        {
+            ["AlarmHistorian:Enabled"] = alarmHistorianEnabled ? "true" : "false",
+            ["ServerHistorian:SqlServer:ConnectionString"] = "Server=localhost;Database=h",
+            ["ServerHistorian:SqlServer:Schema"] = "bad;schema",
+        }).Build();
+
+    /// <summary>
+    ///     An invalid <c>ServerHistorian:SqlServer:Schema</c> must not fail the host when nothing consumes the section:
+    ///     <see cref="HistorianBackendRegistry.Resolve"/> (which Program.cs calls unconditionally) does not throw and
+    ///     the validator does not check it — the same consumer gate the connection string has.
+    /// </summary>
+    [Fact]
+    public void SqlServer_invalid_schema_not_consumed_neither_resolve_nor_validation_fails()
+    {
+        var configuration = BadSchemaConfig(alarmHistorianEnabled: false);
+        var options = new ServerHistorianOptions { Backend = "SqlServer" };
+
+        Should.NotThrow(() => HistorianBackendRegistry.Resolve(options, configuration));
+        new ServerHistorianOptionsValidator(configuration).Validate(null, options).Failed.ShouldBeFalse();
+    }
+
+    /// <summary>Consumed (here by AlarmHistorian alone), the same invalid schema is a named validator error.</summary>
+    [Fact]
+    public void SqlServer_invalid_schema_consumed_is_a_validator_error_naming_the_key()
+    {
+        var configuration = BadSchemaConfig(alarmHistorianEnabled: true);
+        var options = new ServerHistorianOptions { Backend = "SqlServer" };
+
+        Should.NotThrow(() => HistorianBackendRegistry.Resolve(options, configuration));
+        var result = new ServerHistorianOptionsValidator(configuration).Validate(null, options);
+        result.Failed.ShouldBeTrue();
+        result.Failures.ShouldContain(f => f.Contains("ServerHistorian:SqlServer:Schema"));
+    }
 }