diff --git a/src/BizHawk.Emulation.Cores/Waterbox/LibNymaCore.cs b/src/BizHawk.Emulation.Cores/Waterbox/LibNymaCore.cs
index ae51b12cf8..9a8d436db2 100644
--- a/src/BizHawk.Emulation.Cores/Waterbox/LibNymaCore.cs
+++ b/src/BizHawk.Emulation.Cores/Waterbox/LibNymaCore.cs
@@ -176,8 +176,13 @@ namespace BizHawk.Emulation.Cores.Waterbox
 			[MarshalAs(UnmanagedType.ByValArray, SizeConst = 101)]
 			public Track[] Tracks;
 		}
+		/// <summary>
+		/// Callback to receive a disk TOC
+		/// </summary>
+		/// <param name="disk"></param>
+		/// <param name="dest">Deposit a LibNymaCore.TOC here</param>
 		[UnmanagedFunctionPointer(CC)]
-		public delegate void CDTOCCallback(int disk, [In, Out]TOC toc);
+		public delegate void CDTOCCallback(int disk, IntPtr dest);
 		[UnmanagedFunctionPointer(CC)]
 		public delegate void CDSectorCallback(int disk, int lba, IntPtr dest);
 		[BizImport(CC)]
diff --git a/src/BizHawk.Emulation.Cores/Waterbox/NymaCore.Cd.cs b/src/BizHawk.Emulation.Cores/Waterbox/NymaCore.Cd.cs
index 031586300e..a51332274b 100644
--- a/src/BizHawk.Emulation.Cores/Waterbox/NymaCore.Cd.cs
+++ b/src/BizHawk.Emulation.Cores/Waterbox/NymaCore.Cd.cs
@@ -32,9 +32,11 @@ namespace BizHawk.Emulation.Cores.Waterbox
 			}
 		}
 
-		private void CDTOCCallback(int disk, [In, Out]LibNymaCore.TOC t)
+		private void CDTOCCallback(int disk, IntPtr dest)
 		{
-			SetupTOC(t, _disks[disk].TOC);
+			var toc = new LibNymaCore.TOC { Tracks = new LibNymaCore.TOC.Track[101] };
+			SetupTOC(toc, _disks[disk].TOC);
+			Marshal.StructureToPtr(toc, dest, false);
 		}
 		private void CDSectorCallback(int disk, int lba, IntPtr dest)
 		{