diff --git a/debian/lmcp/build-deb.sh b/debian/lmcp/build-deb.sh
index 676f67dd3f..e72419490a 100755
--- a/debian/lmcp/build-deb.sh
+++ b/debian/lmcp/build-deb.sh
@@ -12,6 +12,12 @@ PKGREL=1
 LMCP_TARBALL_SHA256=80a37fc41633ae285b86f2f6cdd97f0c922c03022dce09addd47aeb379f2bcff
 HERE=$(dirname "$(readlink -f "$0")")
 
+# Reproducible build: pin all file mtimes + ar member timestamps to a fixed
+# epoch tied to this packaging release (lmcp v0.3.0 — 2026-04-14 22:00 UTC).
+# Without this, repeat builds produce different byte streams and reprepro
+# refuses re-includes with "size expected: X, got: Y".
+export SOURCE_DATE_EPOCH=1776200400
+
 work=$(mktemp -d)
 trap "rm -rf $work" EXIT