diff --git a/vm/memblock.c b/vm/memblock.c
index e92a4b7..cce6dbe 100644
--- a/vm/memblock.c
+++ b/vm/memblock.c
@@ -252,7 +252,12 @@ static phys_addr_t do_alloc(size_t size, phys_addr_t align)
 			base += align;
 		}
 
-		size_t region_size = it.it_limit - base + 1;
+		size_t region_size = 0;
+
+		if (it.it_limit > base) {
+			region_size = it.it_limit - base + 1;
+		}
+
 		if (region_size >= size) {
 			allocated_base = it.it_base;
 			allocated_limit = base + size;
@@ -376,8 +381,8 @@ void __next_memory_region(struct memblock_iter *it, struct memblock_type *type_a
 			}
 
 			/* we want the area that is overlapped by both
-			  	region M (m_start - m_end) : The region defined as system memory.
-			  	region R (r_start - r_end) : The region defined as free / outside of any reserved regions.
+				region M (m_start - m_end) : The region defined as system memory.
+				region R (r_start - r_end) : The region defined as free / outside of any reserved regions.
 			 */
 			it->it_base = MAX(m_start, r_start);
 			it->it_limit = MIN(m_end, r_end);