diff -Nru nauty-2.6r10+ds/debian/changelog nauty-2.6r10+ds/debian/changelog
--- nauty-2.6r10+ds/debian/changelog	2020-02-27 13:06:14.000000000 -0500
+++ nauty-2.6r10+ds/debian/changelog	2020-11-09 13:17:32.000000000 -0500
@@ -1,3 +1,11 @@
+nauty (2.6r10+ds-1ubuntu2) focal; urgency=medium
+
+  * debian/patches/upstream-biplabg.patch
+    - New patch; fix "sorry, this program doesn't support digraphs yet"
+      message when running nauty-biplabg (LP: #1903548).
+
+ -- Doug Torrance <dtorrance@piedmont.edu>  Mon, 09 Nov 2020 13:17:32 -0500
+
 nauty (2.6r10+ds-1ubuntu1) focal; urgency=medium
 
   * debian/tests/control: in the make-check drop restriction
diff -Nru nauty-2.6r10+ds/debian/patches/series nauty-2.6r10+ds/debian/patches/series
--- nauty-2.6r10+ds/debian/patches/series	2017-11-24 11:17:42.000000000 -0500
+++ nauty-2.6r10+ds/debian/patches/series	2020-11-09 13:12:17.000000000 -0500
@@ -3,6 +3,7 @@
 upstream-zlib-blisstog_c.patch
 upstream-C2help2man.patch
 upstream-autotoolization.patch
+upstream-biplabg.patch
 system-preprocessing-examples.patch
 debianization.patch
 debianization-prefix.patch
diff -Nru nauty-2.6r10+ds/debian/patches/upstream-biplabg.patch nauty-2.6r10+ds/debian/patches/upstream-biplabg.patch
--- nauty-2.6r10+ds/debian/patches/upstream-biplabg.patch	1969-12-31 19:00:00.000000000 -0500
+++ nauty-2.6r10+ds/debian/patches/upstream-biplabg.patch	2020-11-09 13:16:32.000000000 -0500
@@ -0,0 +1,25 @@
+Description: Fix "sorry, this program doesn't support digraphs yet"
+ message when running nauty-biplabg.
+Origin: upstream, http://pallini.di.uniroma1.it/nauty27r1.tar.gz
+Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/nauty/+bug/1903548
+Bug-Macaulay2: https://github.com/Macaulay2/M2/issues/1408
+Last-Update: 2020-11-09
+
+--- a/biplabg.c
++++ b/biplabg.c
+@@ -111,13 +111,13 @@
+ 	    fflush(stderr);
+ 	}
+ 
+-	NODIGRAPHSYET(codetype);
+-
+ 	if (infilename && infilename[0] == '-') infilename = NULL;
+ 	infile = opengraphfile(infilename,&codetype,FALSE,1);
+ 	if (!infile) exit(1);
+ 	if (!infilename) infilename = "stdin";
+ 
++	NODIGRAPHSYET(codetype);
++
+ 	if (!outfilename || outfilename[0] == '-')
+ 	{
+ 	    outfilename = "stdout";