diff --git a/scripts/check-phase19.4.sh b/scripts/check-phase19.4.sh
index ad36d25c..d48b52f1 100755
--- a/scripts/check-phase19.4.sh
+++ b/scripts/check-phase19.4.sh
@@ -50,7 +50,8 @@
 # Environment overrides (default: the sibling checkouts next to this
 # repository): PHASE194_ROOT (this repository), OAUTHSERVER_PLUGIN,
 # USER_PLUGIN, FONOTEKA (the application workspace), PHASE194_USER_BASE
-# (the user plugin commit the additive check compares against).
+# (the space-separated user plugin commits the additive check compares
+# against).
 set -euo pipefail
 
 unset FORCE_COLOR
@@ -60,8 +61,9 @@ ROOT="${PHASE194_ROOT:-$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)}"
 OAUTHSERVER_PLUGIN="${OAUTHSERVER_PLUGIN:-$ROOT/../sm-oauthserver-plugin}"
 FONOTEKA="${FONOTEKA:-$ROOT/../fono""teka.go}"
 USER_PLUGIN="${USER_PLUGIN:-$FONOTEKA/plugins/golem15/user}"
-# The user plugin's last commit before this phase (19-04).
-USER_BASE="${PHASE194_USER_BASE:-c077029}"
+# The user plugin's commits before this phase: the local tip (19-04) and
+# origin's tip, which a later merge joined.
+USER_BASE="${PHASE194_USER_BASE:-c077029 24b16b1}"
 
 # ---------------------------------------------------------------------------
 # Required test names. Each list runs with -run '^(a|b|...)$' and every name
@@ -446,21 +448,33 @@ run_userplugin() {
 	go_named "$FONOTEKA" ./plugins/golem15/user -short "${USER_ROOT_TESTS[@]}"
 	# D-05: additive only. git's status is captured before any filtering, so
 	# an unknown base or a broken checkout fails here instead of reading as
-	# an empty diff.
-	local diff rc=0 removed
-	diff="$(git -C "$USER_PLUGIN" diff "$USER_BASE" -- '*.go' ':(exclude)*_test.go' 2>&1)" || rc=$?
-	if [[ "$rc" -ne 0 ]]; then
-		printf '%s\n' "$diff" | tail -n 5 >&2
-		echo "refuse: git diff $USER_BASE in $USER_PLUGIN failed (exit $rc)" >&2
-		return 1
-	fi
-	removed="$(removed_exports <<<"$diff")"
+	# an empty diff. A declaration counts as removed only when it is removed
+	# against every base (origin's pre-phase commit changed signatures the
+	# local tip still had, and the merge carries that change).
+	local base diff rc removed="" found first=1 added=0
+	for base in $USER_BASE; do
+		rc=0
+		diff="$(git -C "$USER_PLUGIN" diff "$base" -- '*.go' ':(exclude)*_test.go' 2>&1)" || rc=$?
+		if [[ "$rc" -ne 0 ]]; then
+			printf '%s\n' "$diff" | tail -n 5 >&2
+			echo "refuse: git diff $base in $USER_PLUGIN failed (exit $rc)" >&2
+			return 1
+		fi
+		found="$(removed_exports <<<"$diff")"
+		if [[ "$first" -eq 1 ]]; then
+			removed="$found"
+			added="$(grep -cE '^\+(func|type) ' <<<"$diff" || true)"
+			first=0
+		elif [[ -n "$removed" ]]; then
+			removed="$(grep -Fxf <(printf '%s\n' "$found") <<<"$removed" || true)"
+		fi
+	done
 	if [[ -n "$removed" ]]; then
 		printf '%s\n' "$removed" >&2
 		echo "refuse: the user plugin removed or changed exported declarations since $USER_BASE (D-05: additive only)" >&2
 		return 1
 	fi
-	echo "additive: no exported func, method or type removed from the user plugin since $USER_BASE ($(grep -cE '^\+(func|type) ' <<<"$diff" || true) declarations added)"
+	echo "additive: no exported func, method or type removed from the user plugin since $USER_BASE ($added declarations added)"
 	echo "phase19.4 userplugin passed"
 }