diff --git a/ATxCommon/Serializables/DriveToCheck.cs b/ATxCommon/Serializables/DriveToCheck.cs
index 6411bdbc36d8354cdcca054cba9a69872ccc6ef3..a836ec32f9f93bd8d0fd393054e4ca7d2d00cf0f 100644
--- a/ATxCommon/Serializables/DriveToCheck.cs
+++ b/ATxCommon/Serializables/DriveToCheck.cs
@@ -1,4 +1,6 @@
-namespace ATxCommon.Serializables
+using System.Xml.Serialization;
+
+namespace ATxCommon.Serializables
 {
     /// <summary>
     /// Helper class for the nested SpaceMonitoring sections.
@@ -14,5 +16,11 @@
         /// Limit (in GB) of free space, lower values will trigger a notification.
         /// </summary>
         public long SpaceThreshold { get; set; }
+
+        /// <summary>
+        /// Free space of a drive in bytes, set to -1 if unknown or check resulted in an error.
+        /// </summary>
+        [XmlIgnore]
+        public long FreeSpace { get; set; } = -1;
     }
 }
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