diff --git a/core/mem.c b/core/mem.c
index 09712a0..19bea4a 100644
--- a/core/mem.c
+++ b/core/mem.c
@@ -8,10 +8,10 @@ static struct mem_desc *used_page;
 static unsigned long bottom_mem;
 static unsigned long top_mem;
 
-
 int memSetup(unsigned long upper_mem)
 {
-	printf("Free Mem going from %d to %d\n", &__ld_kernel_end, upper_mem * 1024);
+	printf("Free Mem from %d to %d\n", &__ld_kernel_end, upper_mem * 1024);
+	// Memory description is stored after the kernel. We need some place to store it
 	unsigned long memdesc_end =
 	    (unsigned long)page_desc +
 	    ((upper_mem) / (PAGE_SIZE / 1024)) * sizeof(struct mem_desc);
@@ -19,7 +19,7 @@ int memSetup(unsigned long upper_mem)
 	list_init(free_page);
 	list_init(used_page);
 	bottom_mem = lastUsed;
-	top_mem = upper_mem;
+	top_mem    = upper_mem * 1024;
 	for (uint i = 0; i < (upper_mem / (PAGE_SIZE / 1024)); i++) {
 		struct mem_desc *mem = &page_desc[i];
 		if (i < lastUsed) {
@@ -38,15 +38,16 @@ struct mem_desc *addr2memDesc(unsigned long addr)
 {
 	if (addr > top_mem || addr < bottom_mem)
 		return NULL;
+
 	int idx = addr >> PAGE_SHIFT;
 	return page_desc + idx;
 }
 
-
 unsigned long allocPage(void)
 {
-	if (list_is_empty(free_page))
+	if (list_is_empty(free_page)) {
 		return (unsigned long)NULL;
+	}
 	struct mem_desc *mem = list_pop_head(free_page);
 	mem->ref             = 1;
 	list_add_tail(used_page, mem);
@@ -61,6 +62,7 @@ int unrefPage(unsigned long addr)
 	}
 	mem->ref--;
 	if (mem->ref == 0) {
+		list_delete(used_page, mem);
 		list_add_tail(free_page, mem);
 	}
 
diff --git a/tests/test.c b/tests/test.c
index 4fad5e4..c1271bf 100644
--- a/tests/test.c
+++ b/tests/test.c
@@ -1,7 +1,46 @@
+#include "list.h"
+#include "mem.h"
 #include "serial.h"
 #include "vga.h"
 
-void run_test(){
+static void testPhymem()
+{
+	printf("Testing memory PHY\n");
+	struct mem_desc *allocated_page_list;
+	struct mem_desc
+	    *page; // Cast in mem_desc to use it. In fact it's the addr of 4K free memory
+	list_init(allocated_page_list);
+	int allocCount = 0;
+	int freeCount  = 0;
+
+	while ((page = (struct mem_desc *)allocPage()) != NULL) {
+		page->phy_addr = allocCount;
+		allocCount++;
+		list_add_tail(allocated_page_list, page);
+	}
+	printf("%d pages allocated\n", allocCount);
+
+	while ((page = list_pop_head(allocated_page_list)) != NULL) {
+		if (page->phy_addr != (ulong)freeCount) {
+			printf("Error page %d modified\n", (ulong)page);
+		}
+		if (unrefPage((ulong)page)) {
+			printf("Failed to free page %d\n", (ulong)page);
+		}
+		freeCount++;
+	}
+	printf("%d pages freed\n", freeCount);
+
+	if ((page = (struct mem_desc *)allocPage()) == NULL) {
+		printf("Error ! Cannot allocate memory\n");
+	} else {
+		unrefPage((ulong)page);
+	}
+}
+
+void run_test()
+{
+	testPhymem();
 	printf("Testing Serial");
 	serialWrite('h');
 	serialWrite('e');