diff --git a/hw/block/nvme-subsys.c b/hw/block/nvme-subsys.c
index af4804a819..9fadef8cec 100644
--- a/hw/block/nvme-subsys.c
+++ b/hw/block/nvme-subsys.c
@@ -47,15 +47,18 @@ int nvme_subsys_register_ns(NvmeNamespace *ns, Error **errp)
 {
     NvmeSubsystem *subsys = ns->subsys;
     NvmeCtrl *n;
+    uint32_t nsid = nvme_nsid(ns);
     int i;
 
-    if (subsys->namespaces[nvme_nsid(ns)]) {
+    assert(nsid && nsid <= NVME_SUBSYS_MAX_NAMESPACES);
+
+    if (subsys->namespaces[nsid]) {
         error_setg(errp, "namespace %d already registerd to subsy %s",
                    nvme_nsid(ns), subsys->parent_obj.id);
         return -1;
     }
 
-    subsys->namespaces[nvme_nsid(ns)] = ns;
+    subsys->namespaces[nsid] = ns;
 
     for (i = 0; i < ARRAY_SIZE(subsys->ctrls); i++) {
         n = subsys->ctrls[i];
diff --git a/hw/block/nvme-subsys.h b/hw/block/nvme-subsys.h
index fb66ae752a..aafa04b848 100644
--- a/hw/block/nvme-subsys.h
+++ b/hw/block/nvme-subsys.h
@@ -54,6 +54,8 @@ static inline NvmeNamespace *nvme_subsys_ns(NvmeSubsystem *subsys,
         return NULL;
     }
 
+    assert(nsid && nsid <= NVME_SUBSYS_MAX_NAMESPACES);
+
     return subsys->namespaces[nsid];
 }
 
diff --git a/hw/block/nvme.h b/hw/block/nvme.h
index 4955d649c7..5ba2efaedf 100644
--- a/hw/block/nvme.h
+++ b/hw/block/nvme.h
@@ -236,12 +236,18 @@ static inline bool nvme_ns_is_attached(NvmeCtrl *n, NvmeNamespace *ns)
 
 static inline void nvme_ns_attach(NvmeCtrl *n, NvmeNamespace *ns)
 {
-    n->namespaces[nvme_nsid(ns) - 1] = ns;
+    uint32_t nsid = nvme_nsid(ns);
+    assert(nsid && nsid <= NVME_MAX_NAMESPACES);
+
+    n->namespaces[nsid - 1] = ns;
 }
 
 static inline void nvme_ns_detach(NvmeCtrl *n, NvmeNamespace *ns)
 {
-    n->namespaces[nvme_nsid(ns) - 1] = NULL;
+    uint32_t nsid = nvme_nsid(ns);
+    assert(nsid && nsid <= NVME_MAX_NAMESPACES);
+
+    n->namespaces[nsid - 1] = NULL;
 }
 
 static inline NvmeCQueue *nvme_cq(NvmeRequest *req)