diff --git a/src/AddIns/DisplayBindings/FormsDesigner/Project/Src/Services/TypeDiscoveryService.cs b/src/AddIns/DisplayBindings/FormsDesigner/Project/Src/Services/TypeDiscoveryService.cs
index adc4f90e26..aca6c79988 100644
--- a/src/AddIns/DisplayBindings/FormsDesigner/Project/Src/Services/TypeDiscoveryService.cs
+++ b/src/AddIns/DisplayBindings/FormsDesigner/Project/Src/Services/TypeDiscoveryService.cs
@@ -39,7 +39,9 @@ namespace ICSharpCode.FormsDesigner.Services
 				                     + "excludeGlobalTypes=" + excludeGlobalTypes.ToString());
 				//seek in all assemblies
 				//allow to work designers like columns editor in datagridview
-				foreach (Assembly asm in TypeResolutionService.DesignerAssemblies) {
+				// Searching types can cause additional assemblies to be loaded, so we need to use
+				// ToArray to prevent an exception if the collection changes.
+				foreach (Assembly asm in TypeResolutionService.DesignerAssemblies.ToArray()) {
 					AddDerivedTypes(baseType, asm, types);
 				}
 				LoggingService.Debug("TypeDiscoveryService returns " + types.Count + " types");
diff --git a/src/AddIns/Misc/MonoAddIn/Project/Src/MonoGacReferencePanel.cs b/src/AddIns/Misc/MonoAddIn/Project/Src/MonoGacReferencePanel.cs
index 77347bf68d..5bdefdb703 100644
--- a/src/AddIns/Misc/MonoAddIn/Project/Src/MonoGacReferencePanel.cs
+++ b/src/AddIns/Misc/MonoAddIn/Project/Src/MonoGacReferencePanel.cs
@@ -8,6 +8,7 @@
 using ICSharpCode.Build.Tasks;
 using ICSharpCode.SharpDevelop.Gui;
 using System;
+using System.Collections.Generic;
 using System.Windows.Forms;
 
 namespace ICSharpCode.MonoAddIn