diff -Nru dpkg-1.20.5ubuntu1/debian/changelog dpkg-1.20.5ubuntu2/debian/changelog
--- dpkg-1.20.5ubuntu1/debian/changelog	2020-07-28 11:33:55.000000000 +0000
+++ dpkg-1.20.5ubuntu2/debian/changelog	2020-08-31 00:34:46.000000000 +0000
@@ -1,3 +1,12 @@
+dpkg (1.20.5ubuntu2) groovy; urgency=medium
+
+  * scripts/Dpkg/Vendor/Ubuntu.pm: set 'nocheck' in build options by default
+    on Ubuntu/riscv64.  Overridable in debian/rules with
+    'DEB_BUILD_OPTIONS := $(filter-out nocheck,$(DEB_BUILD_OPTIONS))'.
+    LP: #1891686.
+
+ -- Steve Langasek <steve.langasek@ubuntu.com>  Mon, 31 Aug 2020 00:34:46 +0000
+
 dpkg (1.20.5ubuntu1) groovy; urgency=medium
 
   * Merge with Debian; remaining changes:
diff -Nru dpkg-1.20.5ubuntu1/scripts/Dpkg/Vendor/Ubuntu.pm dpkg-1.20.5ubuntu2/scripts/Dpkg/Vendor/Ubuntu.pm
--- dpkg-1.20.5ubuntu1/scripts/Dpkg/Vendor/Ubuntu.pm	2020-06-02 02:51:37.000000000 +0000
+++ dpkg-1.20.5ubuntu2/scripts/Dpkg/Vendor/Ubuntu.pm	2020-08-30 21:06:54.000000000 +0000
@@ -99,12 +99,18 @@
         $self->SUPER::run_hook($hook, $flags);
 
         require Dpkg::BuildOptions;
+	require Dpkg::Arch;
 
 	my $build_opts = Dpkg::BuildOptions->new();
+	my $arch = Dpkg::Arch::get_host_arch();
 
-	if (!$build_opts->has('noopt')) {
-            require Dpkg::Arch;
+	# disable build-time tests by default on riscv64; LP: #1891686
+	if (Dpkg::Arch::debarch_eq($arch, 'riscv64')) {
+	    $build_opts->merge('nocheck', 'riscv64');
+	    $build_opts->export();
+	}
 
+	if (!$build_opts->has('noopt')) {
             my $arch = Dpkg::Arch::get_host_arch();
             if (Dpkg::Arch::debarch_eq($arch, 'ppc64el')) {
 		for my $flag (qw(CFLAGS CXXFLAGS OBJCFLAGS OBJCXXFLAGS GCJFLAGS