diff --git a/src/MonoDevelop.LibraryManager/Updates/UpdatedLibrariesService.cs b/src/MonoDevelop.LibraryManager/Updates/UpdatedLibrariesService.cs
index a7c7b833..b8c1e772 100644
--- a/src/MonoDevelop.LibraryManager/Updates/UpdatedLibrariesService.cs
+++ b/src/MonoDevelop.LibraryManager/Updates/UpdatedLibrariesService.cs
@@ -83,6 +83,10 @@ async Task CheckForUpdatesInternalAsync(Solution solution, CancellationToken can
                 }
 
                 FilePath manifestFileName = project.GetManifestFileName();
+                if (manifestFileName.IsNull)
+                {
+                    continue;
+                }
 
                 List<UpdatedLibraryInfo> manifestUpdates = await SafeGetUpdatesAsync(
                     manifestFileName,