diff --git a/src/kernel/memory/pmm.c b/src/kernel/memory/pmm.c
index e15c4bd..a222e25 100644
--- a/src/kernel/memory/pmm.c
+++ b/src/kernel/memory/pmm.c
@@ -1,25 +1,28 @@
 #include <memory.h>
 
-uint64_t first = 0;
+// Virtual addres of next free page
+uint64_t next = 0;
 
 void pmm_free(uint64_t page)
 {
-  page = (uint64_t)P2V(page);
-  *(uint64_t *)page = first;
-  first = page;
+  // Write previous free pointer to freed page
+  *(uint64_t *)P2V(page) = next;
+  // And update free pointer
+  next = (uint64_t)P2V(page);
 }
 
 uint64_t pmm_alloc()
 {
-  uint64_t page = first;
-  first = page?*(uint64_t *)page:0;
-  page = (uint64_t)(page?V2P(page):0);
-  return page;
+  if(!next) return 0;
+  uint64_t page = next;
+  // Read new free pointer from allocated page
+  next = *(uint64_t *)page;
+  return (uint64_t)V2P(page);
 }
 
 uint64_t pmm_calloc()
 {
   uint64_t page = pmm_alloc();
-  memset(P2V(page), 0, 0x1000);
+  memset(P2V(page), 0, PAGE_SIZE);
   return page;
 }