diff --git a/src/tensors/factorizations.jl b/src/tensors/factorizations.jl
index b6def372..1e37ee92 100644
--- a/src/tensors/factorizations.jl
+++ b/src/tensors/factorizations.jl
@@ -446,8 +446,8 @@ function _compute_svddata!(t::TensorMap, alg::Union{SVD,SDD};
     Udata = SectorDict{I,A}()
     Vdata = SectorDict{I,A}()
     dims = SectorDict{I,Int}()
-    local Σdata
-    if numthreads == 1
+    if numthreads == 1 || length(blocksectors(t)) == 1
+        local Σdata
         for (c, b) in blocks(t)
             U, Σ, V = MatrixAlgebra.svd!(b, alg)
             Udata[c] = U
@@ -481,8 +481,8 @@ function _compute_svddata!(t::TensorMap, alg::Union{SVD,SDD};
         lsc = blocksectors(t)
         lsD3 = map(lsc) do c
             # O(D1^2D2) or O(D1D2^2)
-            return min(size(blocks(t)[c])[1]^2 * size(blocks(t)[c])[2],
-                       size(blocks(t)[c])[1] * size(blocks(t)[c])[2]^2)
+            return min(size(block(t, c), 1)^2 * size(block(t, c), 2),
+                       size(block(t, c), 1) * size(block(t, c), 2)^2)
         end
         lsc = lsc[sortperm(lsD3; rev=true)]
 
@@ -509,13 +509,12 @@ function _compute_svddata!(t::TensorMap, alg::Union{SVD,SDD};
                 Σdata[c] = Σ
                 dims[c] = length(Σ)
                 unlock(Lock)
-            end 
-            errormonitor(task)
+            end
+            return errormonitor(task)
         end
 
         wait.(tasks)
         wait(taskref[])
-
     end
     return Udata, Σdata, Vdata, dims
 end
diff --git a/src/tensors/linalg.jl b/src/tensors/linalg.jl
index 22288f35..e25f518c 100644
--- a/src/tensors/linalg.jl
+++ b/src/tensors/linalg.jl
@@ -246,7 +246,7 @@ function LinearAlgebra.mul!(tC::AbstractTensorMap,
         throw(SpaceMismatch("$(space(tC)) ≠ $(space(tA)) * $(space(tB))"))
     end
 
-    if numthreads == 1
+    if numthreads == 1 || length(blocksectors(tC)) == 1
         for c in blocksectors(tC)
             if hasblock(tA, c) # then also tB should have such a block
                 A = block(tA, c)
@@ -276,10 +276,10 @@ function LinearAlgebra.mul!(tC::AbstractTensorMap,
         lsc = blocksectors(tC)
         lsD3 = map(lsc) do c
             if hasblock(tA, c)
-                return size(blocks(tA)[c], 1) * size(blocks(tA)[c], 2) *
-                       size(blocks(tB)[c], 2)
+                return size(block(tA, c), 1) * size(block(tA, c), 2) *
+                       size(block(tA, c), 2)
             else
-                return size(blocks(tC)[c], 1) * size(blocks(tC)[c], 2)
+                return size(block(tC, c), 1) * size(block(tC, c), 2)
             end
         end
         lsc = lsc[sortperm(lsD3; rev=true)]
diff --git a/src/tensors/vectorinterface.jl b/src/tensors/vectorinterface.jl
index f4d8d873..257ec15f 100644
--- a/src/tensors/vectorinterface.jl
+++ b/src/tensors/vectorinterface.jl
@@ -61,7 +61,7 @@ function VectorInterface.add!(ty::AbstractTensorMap, tx::AbstractTensorMap,
                               α::Number, β::Number;
                               numthreads::Int64=1)
     space(ty) == space(tx) || throw(SpaceMismatch("$(space(ty)) ≠ $(space(tx))"))
-    if numthreads == 1
+    if numthreads == 1 || length(blocksectors) == 1
         for c in blocksectors(tx)
             VectorInterface.add!(block(ty, c), block(tx, c), α, β)
         end
@@ -83,7 +83,7 @@ function VectorInterface.add!(ty::AbstractTensorMap, tx::AbstractTensorMap,
                 c = take!(ch)
                 VectorInterface.add!(block(ty, c), block(tx, c), α, β)
             end
-            return errormonitor(tast)
+            return errormonitor(task)
         end
 
         wait.(tasks)
diff --git a/test/Project.toml b/test/Project.toml
new file mode 100644
index 00000000..5e3ba6a9
--- /dev/null
+++ b/test/Project.toml
@@ -0,0 +1,10 @@
+[deps]
+Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
+ChainRulesTestUtils = "cdddcdb0-9152-4a09-a978-84456f9df70a"
+Combinatorics = "861a8166-3701-5b0c-9a16-15d98fcdc6aa"
+FiniteDifferences = "26cc04aa-876d-5657-8c51-4c34ba976000"
+HalfIntegers = "f0d1745a-41c9-11e9-1dd9-e5d34d218721"
+TensorKit = "07d1fe3e-3e46-537d-9eac-e9e13d0d4cec"
+TestExtras = "5ed8adda-3752-4e41-b88a-e8b09835ee3a"
+WignerSymbols = "9f57e263-0b3d-5e2e-b1be-24f2bb48858b"