diff --git a/CHANGELOG.md b/CHANGELOG.md
index c2d91a090..bac863ac9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/qutip/QuantumToolbox.jl/tree/main)
 
+- Fix CUDA `sparse_to_dense`. ([#386])
+
 ## [v0.25.2]
 Release date: 2025-02-02
 
@@ -104,3 +106,4 @@ Release date: 2024-11-13
 [#378]: https://github.com/qutip/QuantumToolbox.jl/issues/378
 [#380]: https://github.com/qutip/QuantumToolbox.jl/issues/380
 [#383]: https://github.com/qutip/QuantumToolbox.jl/issues/383
+[#386]: https://github.com/qutip/QuantumToolbox.jl/issues/386
diff --git a/ext/QuantumToolboxCUDAExt.jl b/ext/QuantumToolboxCUDAExt.jl
index c8258886b..7a90b27ba 100644
--- a/ext/QuantumToolboxCUDAExt.jl
+++ b/ext/QuantumToolboxCUDAExt.jl
@@ -2,10 +2,12 @@ module QuantumToolboxCUDAExt
 
 using QuantumToolbox
 using QuantumToolbox: makeVal, getVal
-import CUDA: cu, CuArray
-import CUDA.CUSPARSE: CuSparseVector, CuSparseMatrixCSC, CuSparseMatrixCSR
+import CUDA: cu, CuArray, allowscalar
+import CUDA.CUSPARSE: CuSparseVector, CuSparseMatrixCSC, CuSparseMatrixCSR, AbstractCuSparseArray
 import SparseArrays: SparseVector, SparseMatrixCSC
 
+allowscalar(false)
+
 @doc raw"""
     CuArray(A::QuantumObject)
 
@@ -99,10 +101,9 @@ _change_eltype(::Type{T}, ::Val{32}) where {T<:AbstractFloat} = Float32
 _change_eltype(::Type{Complex{T}}, ::Val{64}) where {T<:Union{Int,AbstractFloat}} = ComplexF64
 _change_eltype(::Type{Complex{T}}, ::Val{32}) where {T<:Union{Int,AbstractFloat}} = ComplexF32
 
-sparse_to_dense(::Type{T}, A::CuArray{T}) where {T<:Number} = A
-sparse_to_dense(::Type{T1}, A::CuArray{T2}) where {T1<:Number,T2<:Number} = CuArray{T1}(A)
-sparse_to_dense(::Type{T}, A::CuSparseVector) where {T<:Number} = CuArray{T}(A)
-sparse_to_dense(::Type{T}, A::CuSparseMatrixCSC) where {T<:Number} = CuArray{T}(A)
-sparse_to_dense(::Type{T}, A::CuSparseMatrixCSR) where {T<:Number} = CuArray{T}(A)
+QuantumToolbox.sparse_to_dense(A::MT) where {MT<:AbstractCuSparseArray} = CuArray(A)
+
+QuantumToolbox.sparse_to_dense(::Type{T1}, A::CuArray{T2}) where {T1<:Number,T2<:Number} = CuArray{T1}(A)
+QuantumToolbox.sparse_to_dense(::Type{T}, A::AbstractCuSparseArray) where {T<:Number} = CuArray{T}(A)
 
 end
diff --git a/src/qobj/functions.jl b/src/qobj/functions.jl
index 3ed38394e..8fd805b70 100644
--- a/src/qobj/functions.jl
+++ b/src/qobj/functions.jl
@@ -119,9 +119,6 @@ Converts a sparse QuantumObject to a dense QuantumObject.
 """
 sparse_to_dense(A::QuantumObject) = QuantumObject(sparse_to_dense(A.data), A.type, A.dimensions)
 sparse_to_dense(A::MT) where {MT<:AbstractSparseArray} = Array(A)
-for op in (:Transpose, :Adjoint)
-    @eval sparse_to_dense(A::$op{T,<:AbstractSparseMatrix}) where {T<:BlasFloat} = Array(A)
-end
 sparse_to_dense(A::MT) where {MT<:AbstractArray} = A
 
 sparse_to_dense(::Type{T}, A::AbstractSparseArray) where {T<:Number} = Array{T}(A)
diff --git a/test/ext-test/gpu/cuda_ext.jl b/test/ext-test/gpu/cuda_ext.jl
index 5ed3ce18c..262ae88ed 100644
--- a/test/ext-test/gpu/cuda_ext.jl
+++ b/test/ext-test/gpu/cuda_ext.jl
@@ -1,4 +1,7 @@
 @testset "CUDA Extension" verbose = true begin
+    # Test that scalar indexing is disallowed
+    @test_throws ErrorException CUDA.rand(1)[1]
+
     ψdi = Qobj(Int64[1, 0])
     ψdf = Qobj(Float64[1, 0])
     ψdc = Qobj(ComplexF64[1, 0])
@@ -63,6 +66,21 @@
     @test typeof(CuSparseMatrixCSR(Xsc).data) == CuSparseMatrixCSR{ComplexF64,Int32}
     @test typeof(CuSparseMatrixCSR{ComplexF32}(Xsc).data) == CuSparseMatrixCSR{ComplexF32,Int32}
 
+    # Sparse To Dense
+    # @test sparse_to_dense(cu(ψsi; word_size = 64)).data isa CuVector{Int64} # TODO: Fix this in CUDA.jl
+    @test sparse_to_dense(cu(ψsf; word_size = 64)).data isa CuVector{Float64}
+    @test sparse_to_dense(cu(ψsc; word_size = 64)).data isa CuVector{ComplexF64}
+    # @test sparse_to_dense(cu(Xsi; word_size = 64)).data isa CuMatrix{Int64} # TODO: Fix this in CUDA.jl
+    @test sparse_to_dense(cu(Xsf; word_size = 64)).data isa CuMatrix{Float64}
+    @test sparse_to_dense(cu(Xsc; word_size = 64)).data isa CuMatrix{ComplexF64}
+
+    # @test sparse_to_dense(Int32, cu(ψsf; word_size = 64)).data isa CuVector{Int32} # TODO: Fix this in CUDA.jl
+    # @test sparse_to_dense(Float32, cu(ψsf; word_size = 64)).data isa CuVector{Float32} # TODO: Fix this in CUDA.jl
+    # @test sparse_to_dense(ComplexF32, cu(ψsf; word_size = 64)).data isa CuVector{ComplexF32} # TODO: Fix this in CUDA.jl
+    # @test sparse_to_dense(Int64, cu(Xsf; word_size = 32)).data isa CuMatrix{Int64} # TODO: Fix this in CUDA.jl
+    # @test sparse_to_dense(Float64, cu(Xsf; word_size = 32)).data isa CuMatrix{Float64} # TODO: Fix this in CUDA.jl
+    # @test sparse_to_dense(ComplexF64, cu(Xsf; word_size = 32)).data isa CuMatrix{ComplexF64} # TODO: Fix this in CUDA.jl
+
     # brief example in README and documentation
     N = 20
     ω64 = 1.0    # Float64
diff --git a/test/runtests.jl b/test/runtests.jl
index 97d4b9736..21d133dbe 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -70,7 +70,7 @@ if (GROUP == "CUDA_Ext")# || (GROUP == "All")
     using QuantumToolbox
     using CUDA
     using CUDA.CUSPARSE
-    CUDA.allowscalar(false) # Avoid unexpected scalar indexing
+    # CUDA.allowscalar(false) # This is already set in the extension script
 
     QuantumToolbox.about()
     CUDA.versioninfo()