diff --git a/src/tensors/abstracttensor.jl b/src/tensors/abstracttensor.jl
index 839b260bf..330092aff 100644
--- a/src/tensors/abstracttensor.jl
+++ b/src/tensors/abstracttensor.jl
@@ -308,6 +308,15 @@ function adjointtensorindices(t, p::Index2Tuple)
     return (adjointtensorindices(t, p[1]), adjointtensorindices(t, p[2]))
 end
 
+"""
+    isdual(x::AbstractTensorMap) -> Vector{Bool}
+
+Returns a Boolean vector indicating which spaces of `x` are dual spaces.
+"""
+function isdual(x::AbstractTensorMap)
+    return [isdual(space(x, i)) for i in 1:numind(x)]
+end
+
 # tensor characteristics: work on instances and pass to type
 #------------------------------------------------------------
 InnerProductStyle(t::AbstractTensorMap) = InnerProductStyle(typeof(t))
diff --git a/test/tensors/construction.jl b/test/tensors/construction.jl
index c6047b8d8..2c08b4596 100644
--- a/test/tensors/construction.jl
+++ b/test/tensors/construction.jl
@@ -24,6 +24,7 @@ for V in spacelist
                 @test space(t) == (W ← one(W))
                 @test domain(t) == one(W)
                 @test typeof(t) == TensorMap{T, spacetype(t), 5, 0, Vector{T}}
+                @constinferred isdual(t)
                 # Array type input
                 t = @constinferred zeros(Vector{T}, W)
                 @test @constinferred(hash(t)) == hash(deepcopy(t))