diff --git a/src/analysis.jl b/src/analysis.jl
index 688454371..722ab4186 100644
--- a/src/analysis.jl
+++ b/src/analysis.jl
@@ -101,6 +101,7 @@ the stability region of the complex plane.
 function dcgain(sys::LTISystem, ϵ=0)
     return iscontinuous(sys) ? evalfr(sys, -ϵ) : evalfr(sys, exp(-ϵ*sys.Ts))
 end
+dcgain(G::Union{UniformScaling, Number, AbstractMatrix}) = G
 
 """
     markovparam(sys, n)
diff --git a/src/freqresp.jl b/src/freqresp.jl
index 5dd45e692..e3392cf0a 100644
--- a/src/freqresp.jl
+++ b/src/freqresp.jl
@@ -8,12 +8,14 @@ function freqresp(sys::LTISystem, w::Real)
     evalfr(sys, s)
 end
 
+freqresp(G::Union{UniformScaling, AbstractMatrix, Number}, w::Real) = G
+
 """
     sys_fr = freqresp(sys, w)
 
 Evaluate the frequency response of a linear system
 
-`w -> C*((iw*im -A)^-1)*B + D`
+`w -> C*((iw*im*I - A)^-1)*B + D`
 
 of system `sys` over the frequency vector `w`.
 """
@@ -23,6 +25,14 @@ of system `sys` over the frequency vector `w`.
     [evalfr(sys[i,j], _freq(w, te))[] for w in w_vec, i in 1:ny, j in 1:nu]
 end
 
+@autovec () function freqresp(G::AbstractMatrix, w_vec::AbstractVector{<:Real})
+    repeat(G, 1, 1, length(w_vec))
+end
+
+@autovec () function freqresp(G::Number, w_vec::AbstractVector{<:Real})
+    fill(G, 1, 1, length(w_vec))
+end
+
 _freq(w, ::Continuous) = complex(0, w)
 _freq(w, te::Discrete) = cis(w*te.Ts)
 
@@ -121,6 +131,8 @@ function evalfr(G::TransferFunction{<:TimeEvolution,<:SisoTf}, s::Number)
     map(m -> evalfr(m,s), G.matrix)
 end
 
+evalfr(G::Union{UniformScaling, AbstractMatrix, Number}, s) = G
+
 """
 `F(s)`, `F(omega, true)`, `F(z, false)`
 
diff --git a/src/matrix_comps.jl b/src/matrix_comps.jl
index ac5026b65..2609572d1 100644
--- a/src/matrix_comps.jl
+++ b/src/matrix_comps.jl
@@ -637,7 +637,7 @@ end
 Return the observer_predictor system
 x̂' = (A - KC)x̂ + (B-KD)u + Ky
 ŷ  = Cx + Du
-with the input equation [B K] * [u; y]
+with the input equation [B-KD K] * [u; y]
 
 If covariance matrices `R1, R2` are given, the kalman gain `K` is calculaded.
 
diff --git a/test/test_freqresp.jl b/test/test_freqresp.jl
index 60ffe9d76..cd20c7d13 100644
--- a/test/test_freqresp.jl
+++ b/test/test_freqresp.jl
@@ -34,6 +34,13 @@ resp1 = ones(ComplexF64, length(w), 1, 1)
 @test freqresp(G1, w) == resp1
 @test freqresp(H1, w) == resp1
 
+for G in [2, 2I, 2I(2), randn(2,2)]
+    @test dcgain(G) == G
+    !(G isa UniformScaling) && @test freqresp(G, [1,2]) == cat(G,G, dims=3) # I does not have size
+    @test freqresp(G, 1) == G
+    @test evalfr(G, 1im) == G
+end
+
 ## First order system
 
 sys2 = ss(-1, 1, 1, 1)