diff --git a/OpenRA.Game/Exts.cs b/OpenRA.Game/Exts.cs
index f9cca3b774..06a9f70a38 100644
--- a/OpenRA.Game/Exts.cs
+++ b/OpenRA.Game/Exts.cs
@@ -109,13 +109,23 @@ namespace OpenRA
 
 		public static V GetOrAdd<K, V>(this Dictionary<K, V> d, K k, V v)
 		{
+#if NET5_0_OR_GREATER
+			// SAFETY: Dictionary cannot be modified whilst the ref is alive.
+			ref var value = ref System.Runtime.InteropServices.CollectionsMarshal.GetValueRefOrAddDefault(d, k, out var exists);
+			if (!exists)
+				value = v;
+			return value;
+#else
 			if (!d.TryGetValue(k, out var ret))
 				d.Add(k, ret = v);
 			return ret;
+#endif
 		}
 
 		public static V GetOrAdd<K, V>(this Dictionary<K, V> d, K k, Func<K, V> createFn)
 		{
+			// Cannot use CollectionsMarshal.GetValueRefOrAddDefault here,
+			// the creation function could mutate the dictionary which would invalidate the ref.
 			if (!d.TryGetValue(k, out var ret))
 				d.Add(k, ret = createFn(k));
 			return ret;