diff --git a/Project.toml b/Project.toml
index c0c5e44..d70897d 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "MultivariateOrthogonalPolynomials"
 uuid = "4f6956fd-4f93-5457-9149-7bfc4b2ce06d"
-version = "0.9.1"
+version = "0.9.2"
 
 [deps]
 ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"
diff --git a/src/rect.jl b/src/rect.jl
index 9ee2454..9edeeaf 100644
--- a/src/rect.jl
+++ b/src/rect.jl
@@ -53,8 +53,8 @@ function jacobimatrix(::Val{2}, P::RectPolynomial)
     KronTrav(Y, Eye{eltype(Y)}(∞))
 end
 function diff(P::KronPolynomial{N}, order::NTuple{N,Int}; dims...) where N
-    diffs = diff.(P.args, order)
-    RectPolynomial(basis.(diffs)...) * KronTrav(coefficients.(diffs)...)
+    diffs = map(diff, P.args, order)
+    RectPolynomial(map(basis, diffs)...) * KronTrav(reverse(map(coefficients, diffs))...)
 end
 
 
@@ -164,7 +164,7 @@ end
 
 ## sum
 
-function Base._sum(P::RectPolynomial, dims)
+function Base._sum(P::RectPolynomial, dims::Int)
     @assert dims == 1
     KronTrav(sum.(P.args; dims=1)...)
 end
diff --git a/test/test_rect.jl b/test/test_rect.jl
index b7cf90f..aca9598 100644
--- a/test/test_rect.jl
+++ b/test/test_rect.jl
@@ -155,6 +155,21 @@ using Base: oneto
         @test sum(f) ≈ 10.546408460894801 # empirical
     end
 
+    @testset "diff" begin
+        P = RectPolynomial(Legendre(),Legendre())
+        f = expand(P, splat((x,y) -> 1))
+        @test diff(f,(1,0))[SVector(0.1,0.2)] == diff(f,(0,1))[SVector(0.1,0.2)] == 0.0
+        f = expand(P, splat((x,y) -> x))
+        @test diff(f,(1,0))[SVector(0.1,0.2)] == 1.0
+        @test diff(f,(0,1))[SVector(0.1,0.2)] == 0.0
+        f = expand(P, splat((x,y) -> cos(x*exp(y))))
+        @test diff(f,(1,0))[SVector(0.1,0.2)] ≈ -sin(0.1*exp(0.2))*exp(0.2)
+        @test diff(f,(0,1))[SVector(0.1,0.2)] ≈ -0.1*sin(0.1*exp(0.2))*exp(0.2)
+        @test diff(f,(2,0))[SVector(0.1,0.2)] ≈ -cos(0.1*exp(0.2))*exp(0.4)
+        @test diff(f,(1,1))[SVector(0.1,0.2)] ≈ -sin(0.1*exp(0.2))*exp(0.2) - 0.1*cos(0.1*exp(0.2))*exp(0.4)
+        @test diff(f,(0,2))[SVector(0.1,0.2)] ≈ -0.1*sin(0.1*exp(0.2))*exp(0.2) - 0.1^2*cos(0.1*exp(0.2))*exp(0.4)
+    end
+
     @testset "KronTrav bug" begin
         W = Weighted(Ultraspherical(3/2))
         D² = diff(W)'diff(W)