diff --git a/src/slab.c b/src/slab.c
index 914d8236dd15413e5262e4d989cbda081aa4b637..a39a59860f648db408ea33453d7a78e4122ed5e3 100644
--- a/src/slab.c
+++ b/src/slab.c
@@ -839,7 +839,7 @@ void rt_free(void *ptr)
 		kup->size = 0;
 
 #ifdef RT_MEM_STATS
-		used_mem -= size;
+		used_mem -= size * RT_MM_PAGE_SIZE;
 #endif
 		rt_sem_release(&heap_sem);