diff --git a/src/codegen/gen_java_Message.ysl2 b/src/codegen/gen_java_Message.ysl2
index b84ae29..6a81c51 100644
--- a/src/codegen/gen_java_Message.ysl2
+++ b/src/codegen/gen_java_Message.ysl2
@@ -76,7 +76,7 @@ tstylesheet {
                     }
                 }
 
-                public static int getInstanceCount() {
+                public static synchronized AtomicLong getInstanceCount() {
                     return instanceCount;
                 }