diff --git a/vm/memblock.c b/vm/memblock.c
index c4fb007..14f33ba 100644
--- a/vm/memblock.c
+++ b/vm/memblock.c
@@ -235,8 +235,8 @@ static phys_addr_t do_alloc(size_t size, phys_addr_t align)
 		align = 0x8;
 	}
 
-	/* the base address of the memory region to reserved */
-	phys_addr_t allocated_base = ADDR_MAX;
+	/* the bounds of the memory region to reserve */
+	phys_addr_t allocated_base = ADDR_MAX, allocated_limit = 0;
 	/* the address to return to the caller. may be different from
 	   allocated_base depending on alignment requirements. */
 	phys_addr_t returned_base = ADDR_MAX;
@@ -255,6 +255,7 @@ static phys_addr_t do_alloc(size_t size, phys_addr_t align)
 		size_t region_size = it.it_limit - base + 1;
 		if (region_size >= size) {
 			allocated_base = it.it_base;
+			allocated_limit = base + size;
 			returned_base = base;
 			break;
 		}
@@ -264,7 +265,7 @@ static phys_addr_t do_alloc(size_t size, phys_addr_t align)
 		return 0;
 	}
 
-	int status = memblock_add_range(&memblock.reserved, allocated_base, size, MEMBLOCK_ALLOC);
+	int status = memblock_add_range(&memblock.reserved, allocated_base, allocated_limit - allocated_base, MEMBLOCK_ALLOC);
 	if (status != 0) {
 		return 0;
 	}