diff --git a/src/modules/Elsa.Workflows.Core/Services/ActivityRegistry.cs b/src/modules/Elsa.Workflows.Core/Services/ActivityRegistry.cs
index 9e52e5721..7d732833f 100644
--- a/src/modules/Elsa.Workflows.Core/Services/ActivityRegistry.cs
+++ b/src/modules/Elsa.Workflows.Core/Services/ActivityRegistry.cs
@@ -265,6 +265,7 @@ public class ActivityRegistry(IActivityDescriber activityDescriber, IEnumerable<
     /// <inheritdoc />
     public void Clear()
     {
+        _manualActivityDescriptors.Clear();
         _tenantRegistries.Clear();
         _agnosticRegistry.ActivityDescriptors.Clear();
         _agnosticRegistry.LatestActivityDescriptors.Clear();
diff --git a/test/unit/Elsa.Workflows.Core.UnitTests/Services/ActivityRegistryTests.cs b/test/unit/Elsa.Workflows.Core.UnitTests/Services/ActivityRegistryTests.cs
index 53abb9e50..11f2039f1 100644
--- a/test/unit/Elsa.Workflows.Core.UnitTests/Services/ActivityRegistryTests.cs
+++ b/test/unit/Elsa.Workflows.Core.UnitTests/Services/ActivityRegistryTests.cs
@@ -13,15 +13,16 @@ public class ActivityRegistryTests
     private const string TestActivityType = "TestActivity";
     private const string CurrentTenant = "tenant1";
 
+    private readonly IActivityDescriber _activityDescriber;
     private readonly ILogger<ActivityRegistry> _logger;
     private readonly ActivityRegistry _registry;
 
     public ActivityRegistryTests()
     {
         var tenantAccessor = Substitute.For<ITenantAccessor>();
-        var activityDescriber = Substitute.For<IActivityDescriber>();
+        _activityDescriber = Substitute.For<IActivityDescriber>();
         _logger = Substitute.For<ILogger<ActivityRegistry>>();
-        _registry = new(activityDescriber, [], tenantAccessor, _logger);
+        _registry = new(_activityDescriber, [], tenantAccessor, _logger);
 
         // Set default tenant for all tests
         tenantAccessor.TenantId.Returns(CurrentTenant);
@@ -196,6 +197,25 @@ public class ActivityRegistryTests
         Assert.Null(result);
     }
 
+    [Fact]
+    public async Task GetDescriptorsAsync_ReturnsEmpty_WhenRegistryCleared()
+    {
+        // Arrange
+        _activityDescriber.DescribeActivityAsync(typeof(ActivityRegistryTests), Arg.Any<CancellationToken>())
+            .Returns(Task.FromResult(CreateDescriptor(TestActivityType, 1, CurrentTenant)));
+
+        await _registry.RegisterAsync(typeof(ActivityRegistryTests), CancellationToken.None);
+
+        // Act
+        _registry.Clear();
+        var descriptors = await _registry.GetDescriptorsAsync();
+
+        // Assert
+        Assert.Empty(descriptors);
+        Assert.Empty(_registry.ListAll());
+        Assert.Null(_registry.Find(TestActivityType));
+    }
+
     [Fact]
     public void Find_IgnoresOtherTenantDescriptors_OnlyReturnsCurrentTenantOrAgnostic()
     {
@@ -444,4 +464,4 @@ public class ActivityRegistryTests
         public ValueTask<IEnumerable<ActivityDescriptor>> GetDescriptorsAsync(CancellationToken cancellationToken = default) => new(Descriptors);
     }
 
-}
\ No newline at end of file
+}