diff --git a/src/Marr.Data/Mapping/FluentMappings.cs b/src/Marr.Data/Mapping/FluentMappings.cs
index 8849f1aa1..b05680197 100644
--- a/src/Marr.Data/Mapping/FluentMappings.cs
+++ b/src/Marr.Data/Mapping/FluentMappings.cs
@@ -198,7 +198,8 @@ public RelationshipBuilder<TEntity> AutoMapComplexTypeProperties<T>()
             {
                 return AutoMapPropertiesWhere(m =>
                     m.MemberType == MemberTypes.Property &&
-                    !DataHelper.IsSimpleType((m as PropertyInfo).PropertyType));
+                    !DataHelper.IsSimpleType((m as PropertyInfo).PropertyType) &&
+                    !MapRepository.Instance.TypeConverters.ContainsKey((m as PropertyInfo).PropertyType));
             }
 
             /// <summary>