diff --git a/src/codegen/gen_java_Message.ysl2 b/src/codegen/gen_java_Message.ysl2
index 1cc2404..b84ae29 100644
--- a/src/codegen/gen_java_Message.ysl2
+++ b/src/codegen/gen_java_Message.ysl2
@@ -68,7 +68,7 @@ tstylesheet {
                     instanceCount++;
                 }
 
-                public final void close() {
+                public synchronized final void close() {
                     if(handle != 0) {
                         release(handle);
                         handle = 0;