diff --git a/src/main/java/com/github/hcsp/Stack.java b/src/main/java/com/github/hcsp/Stack.java
index db23e86..aa02d03 100644
--- a/src/main/java/com/github/hcsp/Stack.java
+++ b/src/main/java/com/github/hcsp/Stack.java
@@ -21,6 +21,7 @@ public Object pop() {
         if (size == 0) {
             throw new EmptyStackException();
         }
+        elements[size] = null;
         return elements[--size];
     }