diff --git a/tests/Avalonia.Markup.UnitTests/Properties/AssemblyInfo.cs b/tests/Avalonia.Markup.UnitTests/Properties/AssemblyInfo.cs
index d1567d46be..8adae73fff 100644
--- a/tests/Avalonia.Markup.UnitTests/Properties/AssemblyInfo.cs
+++ b/tests/Avalonia.Markup.UnitTests/Properties/AssemblyInfo.cs
@@ -37,4 +37,5 @@ using Xunit;
 [assembly: AssemblyFileVersion("1.0.0.0")]
 
 // Don't run tests in parallel.
-[assembly: CollectionBehavior(DisableTestParallelization = true)]
\ No newline at end of file
+[assembly: CollectionBehavior(DisableTestParallelization = true)]
+[assembly: CollectionBehavior(MaxParallelThreads = 1)]