diff --git a/compos/common/lib.rs b/compos/common/lib.rs
index 6bea62c..104b8e5 100644
--- a/compos/common/lib.rs
+++ b/compos/common/lib.rs
@@ -18,6 +18,9 @@
 
 pub mod compos_client;
 
+/// Special CID indicating "any".
+pub const VMADDR_CID_ANY: u32 = -1i32 as u32;
+
 /// VSock port that the CompOS server listens on for RPC binder connections. This should be out of
 /// future port range (if happens) that microdroid may reserve for system components.
 pub const COMPOS_VSOCK_PORT: u32 = 6432;