diff --git a/service/history/transferQueueActiveTaskExecutor.go b/service/history/transferQueueActiveTaskExecutor.go
index a0b7417e39e..61e3e2d250f 100644
--- a/service/history/transferQueueActiveTaskExecutor.go
+++ b/service/history/transferQueueActiveTaskExecutor.go
@@ -26,6 +26,7 @@ package history
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"time"
 
@@ -495,6 +496,18 @@ func (t *transferQueueActiveTaskExecutor) processSignalExecution(
 	}
 	attributes := initiatedEvent.GetSignalExternalWorkflowExecutionInitiatedEventAttributes()
 
+	if attributes == nil {
+		fmt.Println("####### PANIC")
+		prettyPrint := func(input interface{}) string {
+			binary, _ := json.MarshalIndent(input, "", "  ")
+			return string(binary)
+		}
+		fmt.Printf("%v\n", prettyPrint(initiatedEvent))
+		fmt.Printf("%v\n", prettyPrint(initiatedEvent))
+		fmt.Printf("%v/%v: %v\n", execution.GetWorkflowId(), execution.GetRunId(), prettyPrint(initiatedEvent))
+		fmt.Println("####### PANIC")
+	}
+
 	targetNamespaceEntry, err := t.shard.GetNamespaceRegistry().GetNamespaceByID(namespace.ID(task.TargetNamespaceID))
 	if err != nil {
 		return err