diff --git a/src/Main/Base/Project/Src/Services/ParserService/ParseProjectContent.cs b/src/Main/Base/Project/Src/Services/ParserService/ParseProjectContent.cs
index 7069cc72fe..aeeb5c83bf 100644
--- a/src/Main/Base/Project/Src/Services/ParserService/ParseProjectContent.cs
+++ b/src/Main/Base/Project/Src/Services/ParserService/ParseProjectContent.cs
@@ -128,7 +128,7 @@ namespace ICSharpCode.Core
 			ReferenceProjectItem reference = e.ProjectItem as ReferenceProjectItem;
 			if (reference != null) {
 				try {
-					IProjectContent referencedContent = ProjectContentRegistry.GetProjectContentForReference(reference);
+					IProjectContent referencedContent = ProjectContentRegistry.GetExistingProjectContentForReference(reference);
 					if (referencedContent != null) {
 						ReferencedContents.Remove(referencedContent);
 						OnReferencedContentsChanged(EventArgs.Empty);
diff --git a/src/Main/Base/Project/Src/Services/ParserService/ProjectContentRegistry.cs b/src/Main/Base/Project/Src/Services/ParserService/ProjectContentRegistry.cs
index 11dc3fa775..00dfb7672f 100644
--- a/src/Main/Base/Project/Src/Services/ParserService/ProjectContentRegistry.cs
+++ b/src/Main/Base/Project/Src/Services/ParserService/ProjectContentRegistry.cs
@@ -95,6 +95,28 @@ namespace ICSharpCode.Core
 			}
 		}
 		
+		public static IProjectContent GetExistingProjectContentForReference(ReferenceProjectItem item)
+		{
+			if (item is ProjectReferenceProjectItem) {
+				if (((ProjectReferenceProjectItem)item).ReferencedProject == null)
+				{
+					return null;
+				}
+				return ParserService.GetProjectContent(((ProjectReferenceProjectItem)item).ReferencedProject);
+			}
+			lock (contents) {
+				string itemInclude = item.Include;
+				string itemFileName = item.FileName;
+				if (contents.ContainsKey(itemFileName)) {
+					return contents[itemFileName];
+				}
+				if (contents.ContainsKey(itemInclude)) {
+					return contents[itemInclude];
+				}
+			}
+			return null;
+		}
+		
 		public static IProjectContent GetProjectContentForReference(ReferenceProjectItem item)
 		{
 			if (item is ProjectReferenceProjectItem) {