diff --git a/common/script/script-api/src/main/java/org/thingsboard/script/api/tbel/TbDate.java b/common/script/script-api/src/main/java/org/thingsboard/script/api/tbel/TbDate.java
index 9c360e5c7e..d8c5fb2265 100644
--- a/common/script/script-api/src/main/java/org/thingsboard/script/api/tbel/TbDate.java
+++ b/common/script/script-api/src/main/java/org/thingsboard/script/api/tbel/TbDate.java
@@ -73,7 +73,9 @@ public class TbDate extends Date {
     }
 
     public String toISOString() {
-        return isoDateFormat.format(this);
+        synchronized (TbDate.class) {
+            return isoDateFormat.format(this);
+        }
     }
 
     public String toLocaleString(String locale) {