diff --git a/virtio-devices/src/mem.rs b/virtio-devices/src/mem.rs
index 434401377..9ad21bd90 100644
--- a/virtio-devices/src/mem.rs
+++ b/virtio-devices/src/mem.rs
@@ -270,7 +270,7 @@ impl VirtioMemConfig {
         // in the usable region.
         if addr % self.block_size != 0
             || size == 0
-            || (addr < self.addr || addr + size >= self.addr + self.usable_region_size)
+            || (addr < self.addr || addr + size > self.addr + self.usable_region_size)
         {
             return false;
         }
diff --git a/vmm/src/memory_manager.rs b/vmm/src/memory_manager.rs
index ecbfe8817..798f641ef 100644
--- a/vmm/src/memory_manager.rs
+++ b/vmm/src/memory_manager.rs
@@ -1675,7 +1675,11 @@ impl MemoryManager {
 
         let start_addr = MemoryManager::start_addr(self.guest_memory.memory().last_addr(), true)?;
 
-        if start_addr.checked_add(size.try_into().unwrap()).unwrap() >= self.end_of_ram_area {
+        if start_addr
+            .checked_add((size - 1).try_into().unwrap())
+            .unwrap()
+            > self.end_of_ram_area
+        {
             return Err(Error::InsufficientHotplugRam);
         }