diff --git a/oximeter/oximeter/schema/virtual-machine.toml b/oximeter/oximeter/schema/virtual-machine.toml
index 520a97bba3d..4fcf7e2c7ad 100644
--- a/oximeter/oximeter/schema/virtual-machine.toml
+++ b/oximeter/oximeter/schema/virtual-machine.toml
@@ -17,6 +17,15 @@ versions = [
     { added_in = 1, fields = [ "state", "vcpu_id" ] }
 ]
 
+[[metrics]]
+name = "vmm_vsz"
+description = "Total virtual memory reserved for reasons other than direct access by the virtual machine"
+units = "bytes"
+datum_type = "u64"
+versions = [
+    { added_in = 1, fields = [ ] }
+]
+
 [[metrics]]
 name = "reset"
 description = "Cumulative number of times the virtual machine has been reset"