diff --git a/lumps/dmxgus/gen-ultramid b/lumps/dmxgus/gen-ultramid
index a8a37bfb..f029b16a 100755
--- a/lumps/dmxgus/gen-ultramid
+++ b/lumps/dmxgus/gen-ultramid
@@ -43,6 +43,14 @@ import sys
 import config
 import stats
 
+HEADER_TEXT = """
+# Freedoom GUS config.
+# Autogenerated by the gen-ultramid script.
+# Please do not manually edit this file!
+# The ordering of entries in this file is significant, to work around a
+# bug in Doom's DMX sound library.
+"""
+
 def normalize_stats(stats):
 	"""Normalize the gathered instrument statistics.
 
@@ -154,6 +162,39 @@ def mapping_for_size(size):
 
 	return result
 
+def instrument_patches(mappings):
+	"""Returns list of MIDI instruments in an appropriate order for output.
+
+	The ordering in the output file is important, because of a bug in the
+	DMX sound library; when patches are shared between instruments it is
+	only possible to refer to instruments listed earlier in the file.
+
+	Args:
+	  mappings: List of mappings from instrument ID to leader instrument.
+	Yields:
+	  A tuple containing each MIDI instrument number and patch file name
+	  to load.
+	"""
+	done_instr_ids = set()
+	# Make multiple passes until we've done all the instruments.
+	while len(done_instr_ids) < len(config.GUS_INSTR_PATCHES):
+		made_progress = False
+		for instr_id, name in sorted(config.GUS_INSTR_PATCHES.items()):
+			for mapping in mappings:
+				mapped_instr_id = mapping[instr_id]
+				if (instr_id != mapped_instr_id and
+				    mapped_instr_id not in done_instr_ids):
+					break
+			else:
+				if instr_id not in done_instr_ids:
+					yield instr_id, name
+					done_instr_ids.add(instr_id)
+					made_progress = True
+
+		assert made_progress, (
+			"infinite loop while producing patches list")
+
+
 if len(sys.argv) != 2:
 	print("Usage: %s <filename>" % sys.argv[0])
 	sys.exit(1)
@@ -166,11 +207,9 @@ mappings = (
 )
 
 with open(sys.argv[1], "w") as output:
-	output.write("# Freedoom GUS config.\n"
-	             "# Autogenerated by the gen-ultramid script.\n"
-		     "# Please do not manually edit this file!\n")
+	output.write(HEADER_TEXT.lstrip())
 
-	for instr_id, name in sorted(config.GUS_INSTR_PATCHES.items()):
+	for instr_id, name in instrument_patches(mappings):
 		line = "%i, %i, %i, %i, %i, %s" % (
 			instr_id,
 			mappings[0][instr_id],