diff -r eb7112f467a8 -r 13168094175b lib/browser/build
--- a/lib/browser/build	Thu Jul 15 15:50:32 2021 +0200
+++ b/lib/browser/build	Thu Jul 15 16:01:04 2021 +0200
@@ -63,7 +63,7 @@
 
   rm -rf classes && mkdir classes
 
-  isabelle_jdk javac -d classes -source 7 "${SOURCES[@]}" || \
+  isabelle_jdk javac -d classes -Xlint:-options -source 7 -target 7 "${SOURCES[@]}" || \
     fail "Failed to compile sources"
   isabelle_jdk jar cf "$(platform_path "$TARGET")" -C classes . ||
     fail "Failed to produce $TARGET"