diff --git a/src/Array.jl b/src/Array.jl
index 47a3a04..53239dd 100644
--- a/src/Array.jl
+++ b/src/Array.jl
@@ -194,6 +194,7 @@ Array{T}(op::Op) where {T,Op<:Control} = Array{T,2 * length(Op)}(op)
 Array{T,N}(op::Control) where {T,N} = Array{T,N}(reshape(Matrix{T}(op), fill(2, N)...))
 
 Array{T}(op::SU{N}) where {T,N} = Array{T,2N}(reshape(Matrix{T}(op), fill(2, 2N)...))
+Array{T,M}(op::SU{N}) where {T,N,M} = (M == 2*N) ?  Array{T,2N}(reshape(Matrix{T}(op), fill(2, 2N)...)) : throw(DimensionMismatch("Array representation of SU{$N} has $(2N) dimensions, but $M was solicited"))
 
 # diagonal matrices
 # NOTE efficient multiplication due to no memory swap needed: plain element-wise multiplication