diff --git a/src/types/DelayLtiSystem.jl b/src/types/DelayLtiSystem.jl
index b403c5200..9c12835a8 100644
--- a/src/types/DelayLtiSystem.jl
+++ b/src/types/DelayLtiSystem.jl
@@ -97,7 +97,7 @@ function +(sys::DelayLtiSystem{T}, n::T) where {T<:Number}
     new_D = copy(ssold.D)
     new_D[1:ny, 1:nu] .+= n
 
-    pnew = PartionedStateSpace(StateSpace(ssold.A, ssold.B, ssold.C, new_D, 0.0), ny, nu)
+    pnew = PartionedStateSpace(StateSpace(ssold.A, ssold.B, ssold.C, new_D, Continuous()), ny, nu)
     DelayLtiSystem(pnew, sys.Tau)
 end
 
diff --git a/test/test_delayed_systems.jl b/test/test_delayed_systems.jl
index 779a64a37..d252e6111 100644
--- a/test/test_delayed_systems.jl
+++ b/test/test_delayed_systems.jl
@@ -16,12 +16,17 @@ else
     @test sprint(show, ss(1,1,1,1)*delay(1.0)) == "DelayLtiSystem{Float64,Float64}\n\nP: StateSpace{Continuous,Float64}\nA = \n 1.0\nB = \n 0.0  1.0\nC = \n 1.0\n 0.0\nD = \n 0.0  1.0\n 1.0  0.0\n\nContinuous-time state-space model\n\nDelays: [1.0]\n"
 end
 
-# Extremely baseic tests
+# Extremely basic tests
 @test freqresp(delay(1), ω) ≈ reshape(exp.(-im*ω), length(ω), 1, 1) rtol=1e-15
 @test freqresp(delay(2.5), ω)[:] ≈ exp.(-2.5im*ω) rtol=1e-15
 @test freqresp(3.5*delay(2.5), ω)[:] ≈ 3.5*exp.(-2.5im*ω) rtol=1e-15
 @test freqresp(delay(2.5)*1.5, ω)[:] ≈ exp.(-2.5im*ω)*1.5 rtol=1e-15
 
+# Addition of constant
+@test evalfr(1 + delay(1.0), 0)[] ≈ 2
+@test evalfr(1 - delay(1.0), 0)[] ≈ 0
+@test evalfr([2 -delay(1.0)], 0) ≈ [2 -1]
+
 # Stritcly proper system
 P1 = DelayLtiSystem(ss(-1.0, 1, 1, 0))
 P1_fr = 1 ./ (im*ω .+ 1)