diff --git a/vhost-user-backend/src/handler.rs b/vhost-user-backend/src/handler.rs
index 5d52edc..0d855e7 100644
--- a/vhost-user-backend/src/handler.rs
+++ b/vhost-user-backend/src/handler.rs
@@ -30,7 +30,10 @@ use super::event_loop::{VringEpollError, VringEpollResult};
 use super::vring::VringT;
 use super::GM;
 
-const MAX_MEM_SLOTS: u64 = 32;
+// vhost in the kernel usually supports 509 mem slots.
+// The 509 used to be the KVM limit, it supported 512, but 3 were used
+// for internal purposes (nowadays, it supports more than that).
+const MAX_MEM_SLOTS: u64 = 509;
 
 #[derive(Debug)]
 /// Errors related to vhost-user handler.
diff --git a/vhost-user-backend/tests/vhost-user-server.rs b/vhost-user-backend/tests/vhost-user-server.rs
index d3e6bb7..d8be86d 100644
--- a/vhost-user-backend/tests/vhost-user-server.rs
+++ b/vhost-user-backend/tests/vhost-user-server.rs
@@ -211,7 +211,7 @@ fn vhost_user_client(path: &Path, barrier: Arc<Barrier>) {
     let state = frontend.get_vring_base(0).unwrap();
     frontend.set_vring_base(0, state as u16).unwrap();
 
-    assert_eq!(frontend.get_max_mem_slots().unwrap(), 32);
+    assert_eq!(frontend.get_max_mem_slots().unwrap(), 509);
     let region = VhostUserMemoryRegionInfo::new(0x800000, 0x100000, addr, 0, fd.file().as_raw_fd());
     frontend.add_mem_region(&region).unwrap();
     frontend.remove_mem_region(&region).unwrap();
diff --git a/vhost/src/vhost_user/dummy_backend.rs b/vhost/src/vhost_user/dummy_backend.rs
index 060a344..9d9f977 100644
--- a/vhost/src/vhost_user/dummy_backend.rs
+++ b/vhost/src/vhost_user/dummy_backend.rs
@@ -8,7 +8,7 @@ use super::*;
 
 pub const MAX_QUEUE_NUM: usize = 2;
 pub const MAX_VRING_NUM: usize = 256;
-pub const MAX_MEM_SLOTS: usize = 32;
+pub const MAX_MEM_SLOTS: usize = 509;
 pub const VIRTIO_FEATURES: u64 = 0x40000003;
 
 #[derive(Default)]
diff --git a/vhost/src/vhost_user/mod.rs b/vhost/src/vhost_user/mod.rs
index c7aed41..66f8c10 100644
--- a/vhost/src/vhost_user/mod.rs
+++ b/vhost/src/vhost_user/mod.rs
@@ -490,7 +490,7 @@ mod tests {
         frontend.set_vring_err(0, &eventfd).unwrap();
 
         let max_mem_slots = frontend.get_max_mem_slots().unwrap();
-        assert_eq!(max_mem_slots, 32);
+        assert_eq!(max_mem_slots, 509);
 
         let region_file: File = TempFile::new().unwrap().into_file();
         let region =