diff --git a/scripts/start/start_preinstall.sh b/scripts/start/start_preinstall.sh
index f5b6794..31f6d68 100755
--- a/scripts/start/start_preinstall.sh
+++ b/scripts/start/start_preinstall.sh
@@ -47,7 +47,13 @@ startPreInstall()
     installSSLCertificate;
     installSwapfile;
 
-    installLibrePortalImageWebUI;
+    # installLibrePortalAppWebUI builds the WebUI image as its step 1 on a fresh
+    # install (libreportal not yet in the DB). Only build standalone here when
+    # that path will be SKIPPED (libreportal already installed — a rebuild), so a
+    # fresh install doesn't build the same image twice.
+    if [[ "$(dockerCheckAppInstalled libreportal docker)" != "not_installed" ]]; then
+        installLibrePortalImageWebUI;
+    fi
     installLibrePortalAppWebUI;
     installLibrePortalWebUITaskService;