diff --git a/SabreTools.Serialization/Readers/ISO9660.cs b/SabreTools.Serialization/Readers/ISO9660.cs
index 3b3e17e0..f5e125bb 100644
--- a/SabreTools.Serialization/Readers/ISO9660.cs
+++ b/SabreTools.Serialization/Readers/ISO9660.cs
@@ -401,11 +401,8 @@ namespace SabreTools.Serialization.Readers
             var groups = new List<PathTableGroup>();
             foreach (VolumeDescriptor vd in vdSet)
             {
-                if (vd is not BaseVolumeDescriptor bvd)
-                    continue;
-
                 // Parse the path table group in the base volume descriptor
-                var pathTableGroups = ParsePathTableGroup(data, sectorLength, bvd);
+                var pathTableGroups = ParsePathTableGroup(data, sectorLength, vd);
                 if (pathTableGroups.Count > 0)
                     groups.AddRange(pathTableGroups);
             }
@@ -424,17 +421,33 @@ namespace SabreTools.Serialization.Readers
         /// <param name="sectorLength">Number of bytes in a logical sector (usually 2048)</param>
         /// <param name="vd">Primary/Supplementary/Enhanced Volume Descriptor pointing to path table(s)</param>
         /// <returns>Filled list of PathTableGroup on success, null on error</returns>
-        public static List<PathTableGroup> ParsePathTableGroup(Stream data, short sectorLength, BaseVolumeDescriptor vd)
+        public static List<PathTableGroup> ParsePathTableGroup(Stream data, short sectorLength, VolumeDescriptor vd)
         {
+            int sizeL, sizeB, locationL, locationL2, locationM, locationM2;
+            if (vd is PrimaryVolumeDescriptor pvd)
+            {
+                sizeL = pvd.PathTableSize.LittleEndian;
+                sizeB = pvd.PathTableSize.BigEndian;
+                locationL = pvd.PathTableLocationL;
+                locationL2 = pvd.OptionalPathTableLocationL;
+                locationM = pvd.PathTableLocationM;
+                locationM2 = pvd.OptionalPathTableLocationM;
+            }
+            else if (vd is SupplementaryVolumeDescriptor svd)
+            {
+                sizeL = svd.PathTableSize.LittleEndian;
+                sizeB = svd.PathTableSize.BigEndian;
+                locationL = svd.PathTableLocationL;
+                locationL2 = svd.OptionalPathTableLocationL;
+                locationM = svd.PathTableLocationM;
+                locationM2 = svd.OptionalPathTableLocationM;
+            }
+            else
+            {
+                return [];
+            }
+
             var groups = new List<PathTableGroup>();
-
-            int sizeL = vd.PathTableSize.LittleEndian;
-            int sizeB = vd.PathTableSize.BigEndian;
-            int locationL = vd.PathTableLocationL;
-            int locationL2 = vd.OptionalPathTableLocationL;
-            int locationM = vd.PathTableLocationM;
-            int locationM2 = vd.OptionalPathTableLocationM;
-
             short blockLength = vd.GetLogicalBlockSize(sectorLength);
 
             var groupL = new PathTableGroup();
@@ -575,14 +588,19 @@ namespace SabreTools.Serialization.Readers
             var directories = new Dictionary<int, FileExtent>();
             foreach (VolumeDescriptor vd in vdSet)
             {
-                if (vd is not BaseVolumeDescriptor bvd)
+                DirectoryRecord rootDirectoryRecord;
+                if (vd is PrimaryVolumeDescriptor pvd)
+                    rootDirectoryRecord = pvd.RootDirectoryRecord;
+                else if (vd is SupplementaryVolumeDescriptor svd)
+                    rootDirectoryRecord = svd.RootDirectoryRecord;
+                else
                     continue;
 
                 // Determine logical block size
-                short blockLength = bvd.GetLogicalBlockSize(sectorLength);
+                short blockLength = vd.GetLogicalBlockSize(sectorLength);
 
                 // Parse the root directory pointed to from the base volume descriptor
-                var descriptors = ParseDirectory(data, sectorLength, blockLength, bvd.RootDirectoryRecord, false);
+                var descriptors = ParseDirectory(data, sectorLength, blockLength, rootDirectoryRecord, false);
                 if (descriptors == null || descriptors.Count == 0)
                     continue;