diff --git a/src/controller/execute.jl b/src/controller/execute.jl
index 7ce81ceae..7f6da0cdf 100644
--- a/src/controller/execute.jl
+++ b/src/controller/execute.jl
@@ -58,12 +58,12 @@ julia> u = moveinput!(mpc, ry); round.(u, digits=3)
 """
 function moveinput!(
     mpc::PredictiveController, 
-    ry::Vector = mpc.estim.model.yop, 
-    d ::Vector = mpc.buffer.empty;
-    lastu::Vector = (mpc.buffer.u .= mpc.lastu0 .+ mpc.estim.model.uop),
-    Dhat ::Vector = repeat!(mpc.buffer.D̂, d,  mpc.Hp),
-    Rhaty::Vector = repeat!(mpc.buffer.Ŷ, ry, mpc.Hp),
-    Rhatu::Vector = mpc.Uop,
+    ry::AbstractVector = mpc.estim.model.yop, 
+    d ::AbstractVector = mpc.buffer.empty;
+    lastu::AbstractVector = (mpc.buffer.u .= mpc.lastu0 .+ mpc.estim.model.uop),
+    Dhat ::AbstractVector = repeat!(mpc.buffer.D̂, d,  mpc.Hp),
+    Rhaty::AbstractVector = repeat!(mpc.buffer.Ŷ, ry, mpc.Hp),
+    Rhatu::AbstractVector = mpc.Uop,
     D̂  = Dhat,
     R̂y = Rhaty,
     R̂u = Rhatu
diff --git a/src/general.jl b/src/general.jl
index 87f738e34..c43e138dc 100644
--- a/src/general.jl
+++ b/src/general.jl
@@ -174,7 +174,7 @@ function repeatdiag(A::Hermitian{NT, Diagonal{NT, Vector{NT}}}, n::Int) where {N
 end
 
 "In-place version of `repeat` but for vectors only."
-function repeat!(Y::Vector, a::Vector, n::Int)
+function repeat!(Y::AbstractVector, a::AbstractVector, n::Int)
     na = length(a)
     for i=0:n-1
         # stop if Y is too short, another clearer error is thrown later in the code:
diff --git a/src/predictive_control.jl b/src/predictive_control.jl
index 33ea5e1d5..843978346 100644
--- a/src/predictive_control.jl
+++ b/src/predictive_control.jl
@@ -51,8 +51,8 @@ print_backends(::IO, ::PredictiveController) = nothing
 
 "Functor allowing callable `PredictiveController` object as an alias for `moveinput!`."
 function (mpc::PredictiveController)(
-    ry::Vector = mpc.estim.model.yop, 
-    d ::Vector = mpc.estim.buffer.empty;
+    ry::AbstractVector = mpc.estim.model.yop, 
+    d ::AbstractVector = mpc.estim.buffer.empty;
     kwargs...
 )
     return moveinput!(mpc, ry, d; kwargs...)