diff --git a/src/equations.jl b/src/equations.jl
index 62c5934e2..77be376ca 100644
--- a/src/equations.jl
+++ b/src/equations.jl
@@ -5,7 +5,7 @@ hide_lhs(_) = false
 ###
 ### Connection
 ###
-struct Connection
+struct Connection <: Real
     systems
 end
 Connection() = Connection(nothing)