diff --git a/android/virtmgr/src/aidl.rs b/android/virtmgr/src/aidl.rs
index d7f68b8..190acc7 100644
--- a/android/virtmgr/src/aidl.rs
+++ b/android/virtmgr/src/aidl.rs
@@ -641,6 +641,24 @@
 
         let calling_partition = find_partition(CALLING_EXE_PATH.as_deref())?;
 
+        let instance_id = extract_instance_id(config);
+        // Require vendor instance IDs to start with a specific prefix so that they don't conflict
+        // with system instance IDs.
+        //
+        // We should also make sure that non-vendor VMs do not use the vendor prefix, but there are
+        // already system VMs in the wild that may have randomly generated IDs with the prefix, so,
+        // for now, we only check in one direction.
+        const INSTANCE_ID_VENDOR_PREFIX: &[u8] = &[0xFF, 0xFF, 0xFF, 0xFF];
+        if matches!(calling_partition, CallingPartition::Vendor | CallingPartition::Odm)
+            && !instance_id.starts_with(INSTANCE_ID_VENDOR_PREFIX)
+        {
+            return Err(anyhow!(
+                "vendor initiated VMs must have instance IDs starting with 0xFFFFFFFF, got {}",
+                hex::encode(instance_id)
+            ))
+            .or_service_specific_exception(-1);
+        }
+
         check_config_features(config)?;
 
         if cfg!(early) {
@@ -668,7 +686,6 @@
             check_gdb_allowed(config)?;
         }
 
-        let instance_id = extract_instance_id(config);
         let mut device_tree_overlays = vec![];
         if let Some(dt_overlay) =
             maybe_create_reference_dt_overlay(config, &instance_id, &temporary_directory)?
diff --git a/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineAppConfig.aidl b/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineAppConfig.aidl
index 5193e21..7db5135 100644
--- a/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineAppConfig.aidl
+++ b/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineAppConfig.aidl
@@ -23,7 +23,11 @@
     /** Name of VM */
     String name;
 
-    /** Id of the VM instance */
+    /**
+     * Id of the VM instance
+     *
+     * See AVirtualMachineRawConfig_setInstanceId for details.
+     */
     byte[64] instanceId;
 
     /** Main APK */
diff --git a/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineRawConfig.aidl b/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineRawConfig.aidl
index c5fe982..1e4fe03 100644
--- a/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineRawConfig.aidl
+++ b/android/virtualizationservice/aidl/android/system/virtualizationservice/VirtualMachineRawConfig.aidl
@@ -31,7 +31,11 @@
     /** Name of VM */
     String name;
 
-    /** Id of the VM instance */
+    /**
+     * Id of the VM instance
+     *
+     * See AVirtualMachineRawConfig_setInstanceId for details.
+     */
     byte[64] instanceId;
 
     /** The kernel image, if any. */
diff --git a/android/virtualizationservice/src/aidl.rs b/android/virtualizationservice/src/aidl.rs
index 1646117..e26cd4f 100644
--- a/android/virtualizationservice/src/aidl.rs
+++ b/android/virtualizationservice/src/aidl.rs
@@ -489,6 +489,9 @@
         id.try_fill(&mut rand::thread_rng())
             .context("Failed to allocate instance_id")
             .or_service_specific_exception(-1)?;
+        // Randomly allocated IDs always start with all 7s to avoid colliding with statically
+        // assigned IDs.
+        id[..4].fill(0x77);
         let uid = get_calling_uid();
         info!("Allocated a VM's instance_id: {:?}..., for uid: {:?}", &hex::encode(id)[..8], uid);
         self.try_updating_sk_state(&id);
diff --git a/libs/libavf/include/android/virtualization.h b/libs/libavf/include/android/virtualization.h
index 4bfe47a..e907ac4 100644
--- a/libs/libavf/include/android/virtualization.h
+++ b/libs/libavf/include/android/virtualization.h
@@ -78,6 +78,9 @@
  * The `instanceId` is expected to be re-used for the VM instance with an associated state (secret,
  * encrypted storage) - i.e., rebooting the VM must not change the instanceId.
  *
+ * `instanceId` MUST start with 0xFFFFFFFF if and only if this library is being
+ * called from code in a vendor or odm partition,
+ *
  * \param config a virtual machine config object.
  * \param instanceId a pointer to a 64-byte buffer for the instance ID.
  * \param instanceIdSize the number of bytes in `instanceId`.