diff --git a/src/main/java/teetime/util/StacklessException.java b/src/main/java/teetime/util/StacklessException.java
index 28adffb30d2d303fa09c45814c909d5e068ecd58..9edf5e3abbb2efb14531b07f50a1111d24e1ecb7 100644
--- a/src/main/java/teetime/util/StacklessException.java
+++ b/src/main/java/teetime/util/StacklessException.java
@@ -15,7 +15,7 @@
  */
 package teetime.util;
 
-public class StacklessException extends RuntimeException {
+public abstract class StacklessException extends RuntimeException {
 
 	private static final long serialVersionUID = -9040980547278981254L;