diff --git a/consul/structs/structs.go b/consul/structs/structs.go
index 531a1e4b8..5b3597bba 100644
--- a/consul/structs/structs.go
+++ b/consul/structs/structs.go
@@ -29,6 +29,7 @@ const (
 	// HealthAny is special, and is used as a wild card,
 	// not as a specific state.
 	HealthAny      = "any"
+	HealthUnknown  = "unknown"
 	HealthPassing  = "passing"
 	HealthWarning  = "warning"
 	HealthCritical = "critical"