diff --git a/include/ucore/slot_allocator.h b/include/ucore/slot_allocator.h
index 55d4eb9..417df05 100644
--- a/include/ucore/slot_allocator.h
+++ b/include/ucore/slot_allocator.h
@@ -4,7 +4,7 @@
 #include <stdint.h>
 #include <assert.h>
 
-// Repurpose free memory to eep a linked list of free slots
+//Free memory is reused to build a linked list of slots
 typedef struct UCSlot UCSlot;
 struct UCSlot {
     UCSlot *next;
@@ -66,6 +66,9 @@ static inline void *uc_slot_alloc(UCSlotArena *arena)
     if (slot != NULL) {
         arena->free_list = slot->next;
         arena->used_slots++;
+#ifdef DEBUG
+        memset(slot, 0xCB, arena->slot_size);
+#endif
     }
 
     return slot;