diff --git a/mcs/class/System.Core/Test/System.Linq.Expressions/ExpressionTest_Coalesce.cs b/mcs/class/System.Core/Test/System.Linq.Expressions/ExpressionTest_Coalesce.cs
index 2ab978d51876f..0fe89ea671075 100644
--- a/mcs/class/System.Core/Test/System.Linq.Expressions/ExpressionTest_Coalesce.cs
+++ b/mcs/class/System.Core/Test/System.Linq.Expressions/ExpressionTest_Coalesce.cs
@@ -163,6 +163,8 @@ public Slot (int v)
 		}
 
 		[Test]
+		// #12987
+		[Category ("MobileNotWorking")]
 		public void CoalesceNullableSlotIntoInteger ()
 		{
 			var s = Expression.Parameter (typeof (Slot?), "s");