--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/file/JRTIndex.java	2026-05-17 21:21:45.925572611 +0100
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/file/JRTIndex.java	2026-05-17 21:23:01.115006534 +0100
@@ -181,7 +181,7 @@
         entries = new HashMap<>();
     }
 
-    public CtSym getCtSym(CharSequence packageName) throws IOException {
+    public synchronized CtSym getCtSym(CharSequence packageName) throws IOException {
         return getEntry(RelativeDirectory.forPackage(packageName)).ctSym;
     }