diff --git a/SabreTools.DatFiles.Test/DatFileTests.Filtering.cs b/SabreTools.DatFiles.Test/DatFileTests.Filtering.cs
index a579a127..feb24011 100644
--- a/SabreTools.DatFiles.Test/DatFileTests.Filtering.cs
+++ b/SabreTools.DatFiles.Test/DatFileTests.Filtering.cs
@@ -62,7 +62,81 @@ namespace SabreTools.DatFiles.Test
 
         #region SetOneRomPerGame
 
-        // TODO: Implement SetOneRomPerGame tests
+        [Fact]
+        public void SetOneRomPerGame_Items()
+        {
+            Source source = new Source(0, source: null);
+
+            Machine machine = new Machine();
+            machine.SetFieldValue(Models.Metadata.Machine.NameKey, "machine");
+
+            DatItem rom = new Rom();
+            rom.SetName("rom.bin");
+            rom.SetFieldValue(DatItem.MachineKey, machine);
+            rom.SetFieldValue(DatItem.SourceKey, source);
+
+            DatItem disk = new Disk();
+            disk.SetName("disk");
+            disk.SetFieldValue(DatItem.MachineKey, machine);
+            disk.SetFieldValue(DatItem.SourceKey, source);
+
+            DatFile datFile = new Logiqx(datFile: null, deprecated: false);
+            datFile.AddItem(rom, statsOnly: false);
+            datFile.AddItem(disk, statsOnly: false);
+
+            datFile.BucketBy(ItemKey.Machine, DedupeType.None);
+            datFile.SetOneRomPerGame();
+
+            var actualDatItems = datFile.GetItemsForBucket("machine");
+            Assert.Equal(2, actualDatItems.Count);
+
+            DatItem actualRom = Assert.Single(actualDatItems.FindAll(i => i is Rom));
+            Machine? actualRomMachine = actualRom.GetFieldValue<Machine>(DatItem.MachineKey);
+            Assert.NotNull(actualRomMachine);
+            Assert.Equal("machine/rom", actualRomMachine.GetStringFieldValue(Models.Metadata.Machine.NameKey));
+
+            DatItem actualDisk = Assert.Single(actualDatItems.FindAll(i => i is Disk));
+            Machine? actualDiskMachine = actualDisk.GetFieldValue<Machine>(DatItem.MachineKey);
+            Assert.NotNull(actualDiskMachine);
+            Assert.Equal("machine/disk", actualDiskMachine.GetStringFieldValue(Models.Metadata.Machine.NameKey));
+        }
+
+        [Fact]
+        public void SetOneRomPerGame_ItemsDB()
+        {
+            Source source = new Source(0, source: null);
+
+            Machine machine = new Machine();
+            machine.SetFieldValue(Models.Metadata.Machine.NameKey, "machine");
+
+            DatItem rom = new Rom();
+            rom.SetName("rom.bin");
+
+            DatItem disk = new Disk();
+            disk.SetName("disk");
+
+            DatFile datFile = new Logiqx(datFile: null, deprecated: false);
+            long sourceIndex = datFile.AddSourceDB(source);
+            long machineIndex = datFile.AddMachineDB(machine);
+            _ = datFile.AddItemDB(rom, machineIndex, sourceIndex, statsOnly: false);
+            _ = datFile.AddItemDB(disk, machineIndex, sourceIndex, statsOnly: false);
+
+            datFile.BucketBy(ItemKey.Machine, DedupeType.None);
+            datFile.SetOneRomPerGame();
+
+            var actualDatItems = datFile.GetItemsForBucketDB("machine");
+            Assert.Equal(2, actualDatItems.Count);
+
+            var actualRom = Assert.Single(actualDatItems, i => i.Value is Rom);
+            var actualRomMachine = datFile.ItemsDB.GetMachineForItem(actualRom.Key);
+            Assert.NotNull(actualRomMachine.Value);
+            Assert.Equal("machine/rom", actualRomMachine.Value.GetStringFieldValue(Models.Metadata.Machine.NameKey));
+
+            var actualDisk = Assert.Single(actualDatItems, i => i.Value is Disk);
+            var actualDiskMachine = datFile.ItemsDB.GetMachineForItem(actualDisk.Key);
+            Assert.NotNull(actualDiskMachine.Value);
+            Assert.Equal("machine/disk", actualDiskMachine.Value.GetStringFieldValue(Models.Metadata.Machine.NameKey));
+        }
 
         #endregion
 
diff --git a/SabreTools.DatFiles/DatFile.Filtering.cs b/SabreTools.DatFiles/DatFile.Filtering.cs
index d3ba71e5..9174c185 100644
--- a/SabreTools.DatFiles/DatFile.Filtering.cs
+++ b/SabreTools.DatFiles/DatFile.Filtering.cs
@@ -433,8 +433,8 @@ namespace SabreTools.DatFiles
         private static void SetOneRomPerGameImpl(DatItem datItem)
         {
             // If the item name is null
-            string? machineName = datItem.GetName();
-            if (machineName == null)
+            string? itemName = datItem.GetName();
+            if (itemName == null)
                 return;
 
             // Get the current machine
@@ -448,19 +448,23 @@ namespace SabreTools.DatFiles
             // Reassign the item to the new machine
             datItem.SetFieldValue<Machine>(DatItem.MachineKey, machine);
 
-            // Remove extensions from Rom items
-            if (datItem is Rom)
+            // Remove extensions from File and Rom items
+            if (datItem is DatItems.Formats.File || datItem is Rom)
             {
-                string[] splitname = machineName.Split('.');
-                machineName = machine.GetStringFieldValue(Models.Metadata.Machine.NameKey)
+                string[] splitname = itemName.Split('.');
+                itemName = machine.GetStringFieldValue(Models.Metadata.Machine.NameKey)
                     + $"/{string.Join(".", splitname, 0, splitname.Length > 1 ? splitname.Length - 1 : 1)}";
             }
+            else
+            {
+                itemName = machine.GetStringFieldValue(Models.Metadata.Machine.NameKey) + $"/{itemName}";
+            }
 
             // Strip off "Default" prefix only for ORPG
-            if (machineName.StartsWith("Default"))
-                machineName = machineName.Substring("Default".Length + 1);
+            if (itemName.StartsWith("Default"))
+                itemName = itemName.Substring("Default".Length + 1);
 
-            machine.SetFieldValue<string?>(Models.Metadata.Machine.NameKey, machineName);
+            machine.SetFieldValue<string?>(Models.Metadata.Machine.NameKey, itemName);
             datItem.SetName(Path.GetFileName(datItem.GetName()));
         }
 
@@ -506,8 +510,8 @@ namespace SabreTools.DatFiles
         private void SetOneRomPerGameImplDB(KeyValuePair<long, DatItem> datItem)
         {
             // If the item name is null
-            string? machineName = datItem.Value.GetName();
-            if (datItem.Key < 0 || machineName == null)
+            string? itemName = datItem.Value.GetName();
+            if (datItem.Key < 0 || itemName == null)
                 return;
 
             // Get the current machine
@@ -522,21 +526,25 @@ namespace SabreTools.DatFiles
                 return;
 
             // Reassign the item to the new machine
-            ItemsDB._itemToMachineMapping[machine.Key] = newMachineIndex;
+            ItemsDB._itemToMachineMapping[datItem.Key] = newMachineIndex;
 
-            // Remove extensions from Rom items
-            if (datItem.Value is Rom)
+            // Remove extensions from File and Rom items
+            if (datItem.Value is DatItems.Formats.File || datItem.Value is Rom)
             {
-                string[] splitname = machineName.Split('.');
-                machineName = machine.Value.GetStringFieldValue(Models.Metadata.Machine.NameKey)
+                string[] splitname = itemName.Split('.');
+                itemName = machine.Value.GetStringFieldValue(Models.Metadata.Machine.NameKey)
                     + $"/{string.Join(".", splitname, 0, splitname.Length > 1 ? splitname.Length - 1 : 1)}";
             }
+            else
+            {
+                itemName = machine.Value.GetStringFieldValue(Models.Metadata.Machine.NameKey) + $"/{itemName}";
+            }
 
             // Strip off "Default" prefix only for ORPG
-            if (machineName.StartsWith("Default"))
-                machineName = machineName.Substring("Default".Length + 1);
+            if (itemName.StartsWith("Default"))
+                itemName = itemName.Substring("Default".Length + 1);
 
-            machine.Value.SetFieldValue<string?>(Models.Metadata.Machine.NameKey, machineName);
+            machine.Value.SetFieldValue<string?>(Models.Metadata.Machine.NameKey, itemName);
             datItem.Value.SetName(Path.GetFileName(datItem.Value.GetName()));
         }