Index: newgrf.c
===================================================================
--- newgrf.c	(revision 4572)
+++ newgrf.c	(working copy)
@@ -1446,6 +1446,17 @@
 			break;
 		}
 
+		/* Deterministic Word-Size Sprite Group */
+		case 0x85: // Self scope, byte
+		case 0x86: // Parent scope, byte
+		/* Deterministic Doubleword-Size Sprite Group */
+		case 0x89: // Self scope, byte
+		case 0x8A: // Parent scope, byte
+		{
+			grfmsg(GMS_WARN, "NewSpriteGroup (0x%02X:0x%02X): No support for deterministic sprite groups using word/doubleword variables, skipping.", setid, type);
+			break;
+		}
+
 		default:
 		{
 			RealSpriteGroup *rg;
@@ -1453,6 +1464,8 @@
 			byte num_loading = grf_load_byte(&buf);
 			uint i;
 
+			check_length(bufend - buf, (num_loaded + num_loading) * 2, "NewSpriteGroup");
+
 			if (_cur_grffile->spriteset_start == 0) {
 				grfmsg(GMS_ERROR, "NewSpriteGroup: No sprite set to work on! Skipping.");
 				return;