diff --git a/Project.toml b/Project.toml
index 07cc086..da525fa 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "ApproxFunOrthogonalPolynomials"
 uuid = "b70543e2-c0d9-56b8-a290-0d4d6d4de211"
-version = "0.5.17"
+version = "0.5.18"
 
 [deps]
 ApproxFunBase = "fbd15aa5-315a-5a7d-a8a4-24992e37be05"
diff --git a/src/Spaces/Chebyshev/ChebyshevOperators.jl b/src/Spaces/Chebyshev/ChebyshevOperators.jl
index f53a7c3..ff103f2 100644
--- a/src/Spaces/Chebyshev/ChebyshevOperators.jl
+++ b/src/Spaces/Chebyshev/ChebyshevOperators.jl
@@ -214,8 +214,10 @@ end
 
 ## Derivative
 
-Derivative(sp::Chebyshev{DD},order::Integer) where {DD<:IntervalOrSegment} =
+function Derivative(sp::Chebyshev{DD},order::Number) where {DD<:IntervalOrSegment}
+    @assert Integer(order) == order "order must be an integer"
     ConcreteDerivative(sp,order)
+end
 
 
 rangespace(D::ConcreteDerivative{Chebyshev{DD,RR}}) where {DD<:IntervalOrSegment,RR} =
diff --git a/src/Spaces/Hermite/Hermite.jl b/src/Spaces/Hermite/Hermite.jl
index 29f5adc..3fd43e1 100644
--- a/src/Spaces/Hermite/Hermite.jl
+++ b/src/Spaces/Hermite/Hermite.jl
@@ -87,8 +87,9 @@ Fun(::typeof(identity), sp::GaussWeight) = Fun(identity, sp.space)
 
 spacescompatible(a::GaussWeight,b::GaussWeight)=spacescompatible(a.space,b.space)&&isapprox(a.L,b.L)
 
-function Derivative(sp::GaussWeight,k::Integer)
-   if k == 1
+function Derivative(sp::GaussWeight,k::Number)
+    @assert Integer(k) == k "order must be an integer"
+    if k == 1
         x = Multiplication(Fun(identity,sp.space),sp.space)
         D = Derivative(sp.space)
         D2 = D - (2sp.L)x
diff --git a/src/Spaces/Jacobi/JacobiOperators.jl b/src/Spaces/Jacobi/JacobiOperators.jl
index 5d52164..0bbc9c4 100644
--- a/src/Spaces/Jacobi/JacobiOperators.jl
+++ b/src/Spaces/Jacobi/JacobiOperators.jl
@@ -1,6 +1,7 @@
 ## Derivative
 
-function Derivative(J::Jacobi,k::Integer)
+function Derivative(J::Jacobi,k::Number)
+    @assert Integer(k) == k "order must be an integer"
     k==1 ? ConcreteDerivative(J,1) :
         DerivativeWrapper(
             TimesOperator(
@@ -33,7 +34,8 @@ Evaluation(S::NormalizedPolynomialSpace{<:Jacobi},x::Number,o::Integer) = Concre
 
 ## Integral
 
-function Integral(J::Jacobi,k::Integer)
+function Integral(J::Jacobi,k::Number)
+    @assert Integer(k) == k "order must be an integer"
     if k > 1
         Q=Integral(J,1)
         IntegralWrapper(TimesOperator(Integral(rangespace(Q),k-1),Q),J,k)
diff --git a/src/Spaces/Ultraspherical/UltrasphericalOperators.jl b/src/Spaces/Ultraspherical/UltrasphericalOperators.jl
index c9769d9..39a0652 100644
--- a/src/Spaces/Ultraspherical/UltrasphericalOperators.jl
+++ b/src/Spaces/Ultraspherical/UltrasphericalOperators.jl
@@ -54,9 +54,12 @@ end
 #Derivative(d::IntervalOrSegment)=Derivative(1,d)
 
 
-Derivative(sp::Ultraspherical{LT,DD},m::Integer) where {LT,DD<:IntervalOrSegment} =
+function Derivative(sp::Ultraspherical{LT,DD}, m::Number) where {LT,DD<:IntervalOrSegment}
+    @assert Integer(m) == m "order must be an integer"
     ConcreteDerivative(sp,m)
-function Integral(sp::Ultraspherical{LT,DD},m::Integer) where {LT,DD<:IntervalOrSegment}
+end
+function Integral(sp::Ultraspherical{LT,DD}, m::Number) where {LT,DD<:IntervalOrSegment}
+    @assert Integer(m) == m "order must be an integer"
     λ = order(sp)
     if m ≤ λ
         ConcreteIntegral(sp,m)