diff --git a/src/types/TransferFunction.jl b/src/types/TransferFunction.jl
index 6695ba9bd..f450aab06 100644
--- a/src/types/TransferFunction.jl
+++ b/src/types/TransferFunction.jl
@@ -24,6 +24,7 @@ end
 
 noutputs(G::TransferFunction) = size(G.matrix, 1)
 ninputs(G::TransferFunction) = size(G.matrix, 2)
+nstates(G::TransferFunction) = length(pole(G)) # Does not work for MIMO 
 
 #####################################################################
 ##                          Misc. Functions                        ##