diff -Nru nauty-2.8.8+ds/debian/changelog nauty-2.8.8+ds/debian/changelog
--- nauty-2.8.8+ds/debian/changelog	2024-04-02 15:21:18.000000000 +0000
+++ nauty-2.8.8+ds/debian/changelog	2024-04-03 12:48:37.000000000 +0000
@@ -1,3 +1,16 @@
+nauty (2.8.8+ds-5) unstable; urgency=medium
+
+  * debian/control
+    - Switch from pkg-config -> pkgconf in libnuaty-dev Build-Depends.
+  * debian/patches/file-offset-bits.patch
+    - New patch; set _FILE_OFFSET_BITS to 64 if AC_SYS_LARGEFILE returns
+      "no".  Fixes build on some architectures after t64 transition.
+  * debian/tests/control
+    - Switch from pkg-config -> pkgconf in Depends for build-examples
+      autopkgtest.
+
+ -- Doug Torrance <dtorrance@debian.org>  Wed, 03 Apr 2024 08:48:37 -0400
+
 nauty (2.8.8+ds-4) unstable; urgency=medium
 
   * debian/control
diff -Nru nauty-2.8.8+ds/debian/control nauty-2.8.8+ds/debian/control
--- nauty-2.8.8+ds/debian/control	2024-04-02 15:16:33.000000000 +0000
+++ nauty-2.8.8+ds/debian/control	2024-04-02 18:52:13.000000000 +0000
@@ -66,7 +66,7 @@
 Pre-Depends: ${misc:Pre-Depends}
 Depends: libnauty-2.8.8 (= ${binary:Version}), ${misc:Depends}
 Conflicts: libnauty2-dev
-Suggests: nauty-doc, pkg-config
+Suggests: nauty-doc, pkgconf
 Multi-Arch: same
 Description: library for graph automorphisms -- development package
  nauty (No AUTomorphisms, Yes?) is a set of procedures for computing
diff -Nru nauty-2.8.8+ds/debian/patches/file-offset-bits.patch nauty-2.8.8+ds/debian/patches/file-offset-bits.patch
--- nauty-2.8.8+ds/debian/patches/file-offset-bits.patch	1970-01-01 00:00:00.000000000 +0000
+++ nauty-2.8.8+ds/debian/patches/file-offset-bits.patch	2024-04-03 12:45:08.000000000 +0000
@@ -0,0 +1,18 @@
+Description: Set _FILE_OFFSET_BITS to 64 if AC_SYS_LARGEFILE returns "no".
+ Otherwise, build fails on some architectures after the t64 transition with
+ "_TIME_BITS=64 is allowed only with _FILE_OFFSET_BITS=64".
+Author: Doug Torrance <dtorrance@debian.org>
+Forwarded: not-needed
+Last-Update: 2024-04-03
+
+--- a/configure.ac
++++ b/configure.ac
+@@ -179,7 +179,7 @@
+ MORECFLAGS=""
+ dnl  we need  AC_SYS_LARGEFILE and AC_FUNC_FSEEKO
+ AC_SYS_LARGEFILE
+-AS_IF([test "x$ac_cv_sys_file_offset_bits" = xno],[ac_cv_sys_file_offset_bits=0])
++AS_IF([test "x$ac_cv_sys_file_offset_bits" = xno],[ac_cv_sys_file_offset_bits=64])
+ AC_SUBST(ac_cv_sys_file_offset_bits)
+ 
+ dnl AS_IF([test "x$user_cflags" = x || test "x$user_cflags" = x-m32],
diff -Nru nauty-2.8.8+ds/debian/patches/series nauty-2.8.8+ds/debian/patches/series
--- nauty-2.8.8+ds/debian/patches/series	2024-04-02 14:51:21.000000000 +0000
+++ nauty-2.8.8+ds/debian/patches/series	2024-04-03 12:36:28.000000000 +0000
@@ -11,3 +11,4 @@
 fall-off.patch
 noreturn.patch
 pkgincludedir.patch
+file-offset-bits.patch
diff -Nru nauty-2.8.8+ds/debian/tests/control nauty-2.8.8+ds/debian/tests/control
--- nauty-2.8.8+ds/debian/tests/control	2024-04-02 15:15:51.000000000 +0000
+++ nauty-2.8.8+ds/debian/tests/control	2024-04-02 17:39:28.000000000 +0000
@@ -2,4 +2,4 @@
 Depends: nauty, tcc, libc6-dev
 
 Tests: build-examples
-Depends: nauty-doc, libnauty-dev, build-essential, pkg-config
+Depends: nauty-doc, libnauty-dev, build-essential, pkgconf