diff --git a/tools/lab/from-package b/tools/lab/from-package
index 78f7cb5..d381a4d 100755
--- a/tools/lab/from-package
+++ b/tools/lab/from-package
@@ -17,11 +17,15 @@ docker exec "$NAME" sh -c '
     chmod +x /usr/sbin/policy-rc.d
     apt-get update -qq >/dev/null 2>&1'
 
+# apt-get install on the file, exactly as ekklesia-classroom-update does.
+# Not dpkg -i and then apt-get -f: when the package conflicts with
+# something installed (khelpcenter, from 0.2.6.2) dpkg refuses, and -f then
+# "fixes" it by dropping the classroom package rather than the conflict —
+# measured, and a lab that installs differently from a classroom tests the
+# wrong thing.
 docker exec "$NAME" sh -c "
-    DEBIAN_FRONTEND=noninteractive dpkg -i '/srv/classroom/${DEB#$ROOT/}' \
-        >/dev/null 2>&1 || true
-    DEBIAN_FRONTEND=noninteractive apt-get -y -qq -f install >/dev/null 2>&1
-    DEBIAN_FRONTEND=noninteractive dpkg --configure ekklesia-classroom >/dev/null 2>&1
+    DEBIAN_FRONTEND=noninteractive apt-get install -y -qq '/srv/classroom/${DEB#$ROOT/}' \
+        >/tmp/from-package-install.log 2>&1 || cat /tmp/from-package-install.log
     rm -f /usr/sbin/policy-rc.d"
 
 state=$(docker exec "$NAME" dpkg-query -W -f='${db:Status-Abbrev}' ekklesia-classroom)