diff --git a/Makefile b/Makefile
index 2ae51bb..194067b 100644
--- a/Makefile
+++ b/Makefile
@@ -42,29 +42,19 @@ deb:
 	# pattern would otherwise be re-used by dpkg-deb if the
 	# previous run left it lying around).
 	rm -f ../postit_*$(POSTIT_GIT_TAG)-1*.deb ../postit_*.buildinfo ../postit_*.changes
-	# Use dpkg-architecture to set the target arch correctly for
-	# cross-builds. For POSTIT_RUNTIME=linux-arm64, this exports
-	# DEB_HOST_ARCH=arm64 (and friends) so dpkg-buildpackage names
-	# the .deb postit_*_arm64.deb instead of postit_*_amd64.deb.
-	# For linux-x64, it sets the host arch to amd64 explicitly
-	# (which matches the runner — no-op, but keeps the call site
-	# uniform). Other RIDs are rejected.
+	# dpkg-buildpackage doesn't know about dotnet's --runtime.
+	# It uses the host arch by default, so cross-compiled builds
+	# end up named '_amd64.deb' regardless of POSTIT_RUNTIME.
+	# -aarm64 forces the .deb to be tagged and named as arm64.
+	# Override DEB_BUILD_GNU_TYPE so dpkg doesn't try to use
+	# arm64 tools on an amd64 host.
 	case "$(POSTIT_RUNTIME)" in
-	    linux-arm64) DPKG_ARCH_ARGS="-aarm64" ;;
-	    linux-x64)   DPKG_ARCH_ARGS="-aamd64" ;;
+	    linux-arm64) DPKG_ARCH=arm64 ;;
+	    linux-x64)   DPKG_ARCH=amd64 ;;
 	    *) echo "  ERROR: unsupported POSTIT_RUNTIME=$(POSTIT_RUNTIME)" >&2; exit 1 ;;
 	esac
-	# dpkg-architecture with no -t/-a flags just prints the arch
-	# info; with -aarm64, it exports the variables needed for a
-	# cross-build targeting arm64. Use 'eval' to put those vars
-	# in the environment of the next command.
-	# Chain 'eval' and 'dpkg-buildpackage' on a single shell line
-	# so the exported vars from dpkg-architecture are visible
-	# to dpkg-buildpackage. Each recipe line runs in its own
-	# shell, so an 'eval' on one line wouldn't affect the next.
-	eval $(dpkg-architecture $$DPKG_ARCH_ARGS) && \
 	POSTIT_GIT_URL=$(POSTIT_GIT_URL) POSTIT_GIT_TAG=$(POSTIT_GIT_TAG) POSTIT_RUNTIME=$(POSTIT_RUNTIME) \
-	    dpkg-buildpackage -us -uc -b
+	    dpkg-buildpackage -us -uc -b -a$$DPKG_ARCH
 	# dpkg-buildpackage already writes the produced .deb to
 	# /src/_src/../ = $POSTIT_OUT_DIR (its default — there's no
 	# flag to change it). So no 'mv' is needed. The old 'mv'