diff --git a/src/lib/Microsoft.Fx.Portability/Reporting/ObjectModel/MissingMemberInfo.cs b/src/lib/Microsoft.Fx.Portability/Reporting/ObjectModel/MissingMemberInfo.cs
index 104078525..65f5604a8 100644
--- a/src/lib/Microsoft.Fx.Portability/Reporting/ObjectModel/MissingMemberInfo.cs
+++ b/src/lib/Microsoft.Fx.Portability/Reporting/ObjectModel/MissingMemberInfo.cs
@@ -12,7 +12,10 @@ public class MissingMemberInfo : MissingInfo
     {
         private readonly HashSet<AssemblyInfo> _usedInAssemblies;
 
-        public IEnumerable<AssemblyInfo> UsedIn { get; }
+        public IEnumerable<AssemblyInfo> UsedIn
+        {
+            get { return _usedInAssemblies.ToList().AsReadOnly(); }
+        }
 
         public int Uses
         {