diff --git a/features-linux.md b/features-linux.md
index 452514387..39df03dad 100644
--- a/features-linux.md
+++ b/features-linux.md
@@ -209,3 +209,21 @@ Irrelevant to the availability of Intel RDT on the host operating system.
   "enabled": true
 }
 ```
+
+## <a name="linuxFeaturesMountExtensions" />MountExtensions
+
+**`mountExtensions`** (object, OPTIONAL) represents the runtime's implementation status of different mount features.
+Irrelevant to the availability of the features on the host operating system.
+
+* **`idmap`** (object, OPTIONAL) represents whether the runtime supports idmap mounts using the uidMappings and gidMappings properties of the mount.
+  * **`enabled`** (bool, OPTIONAL) represents whether the feature is enabled.
+
+### Example
+
+```json
+"mountExtensions": {
+  "idmap":{
+    "enabled": true
+  }
+}
+```
diff --git a/schema/features-linux.json b/schema/features-linux.json
index 723ee67b8..cb01fa862 100644
--- a/schema/features-linux.json
+++ b/schema/features-linux.json
@@ -97,6 +97,19 @@
                         "type": "boolean"
                     }
                 }
+            },
+            "mountExtensions": {
+                "type": "object",
+                "properties": {
+                    "idmap": {
+                        "type": "object",
+                        "properties": {
+			    "enabled": {
+                                "type": "boolean"
+                            }
+                       }
+                    }
+                }
             }
         }
     }
diff --git a/specs-go/features/features.go b/specs-go/features/features.go
index 230e88f56..39009c79d 100644
--- a/specs-go/features/features.go
+++ b/specs-go/features/features.go
@@ -36,11 +36,12 @@ type Linux struct {
 	// Nil value means "unknown", not "no support for any capability".
 	Capabilities []string `json:"capabilities,omitempty"`
 
-	Cgroup   *Cgroup   `json:"cgroup,omitempty"`
-	Seccomp  *Seccomp  `json:"seccomp,omitempty"`
-	Apparmor *Apparmor `json:"apparmor,omitempty"`
-	Selinux  *Selinux  `json:"selinux,omitempty"`
-	IntelRdt *IntelRdt `json:"intelRdt,omitempty"`
+	Cgroup          *Cgroup          `json:"cgroup,omitempty"`
+	Seccomp         *Seccomp         `json:"seccomp,omitempty"`
+	Apparmor        *Apparmor        `json:"apparmor,omitempty"`
+	Selinux         *Selinux         `json:"selinux,omitempty"`
+	IntelRdt        *IntelRdt        `json:"intelRdt,omitempty"`
+	MountExtensions *MountExtensions `json:"mountExtensions,omitempty"`
 }
 
 // Cgroup represents the "cgroup" field.
@@ -123,3 +124,16 @@ type IntelRdt struct {
 	// Nil value means "unknown", not "false".
 	Enabled *bool `json:"enabled,omitempty"`
 }
+
+// MountExtensions represents the "mountExtensions" field.
+type MountExtensions struct {
+	// IDMap represents the status of idmap mounts support.
+	IDMap *IDMap `json:"idmap,omitempty"`
+}
+
+type IDMap struct {
+	// Enabled represents whether idmap mounts supports is compiled in.
+	// Unrelated to whether the host supports it or not.
+	// Nil value means "unknown", not "false".
+	Enabled *bool `json:"enabled,omitempty"`
+}