diff --git a/hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureEvent.java b/hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureEvent.java
index ab1929fb8ce7..63aadcbb4d40 100644
--- a/hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureEvent.java
+++ b/hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureEvent.java
@@ -126,7 +126,7 @@ public ProcedureDeque getSuspendedProcedures() {
   }
 
   @Override
-  public String toString() {
+  public synchronized String toString() {
     return getClass().getSimpleName() + " for " + object + ", ready=" + isReady() + ", "
       + suspendedProcedures;
   }