diff --git a/src/pdf.sandbox.external.js b/src/pdf.sandbox.external.js
index ce77db1c61b39..365d94a609241 100644
--- a/src/pdf.sandbox.external.js
+++ b/src/pdf.sandbox.external.js
@@ -62,6 +62,9 @@ export class SandboxSupportBase {
    * @param {Array<Object>} args - Arguments of the function.
    */
   callSandboxFunction(name, args) {
+    if (!this.commFun) {
+      return;
+    }
     try {
       args = this.exportValueToSandbox(args);
       this.commFun(name, args);