diff --git a/NDTensors/src/lib/Sectors/src/abstractcategory.jl b/NDTensors/src/lib/Sectors/src/abstractcategory.jl
index e05a97d056..374650ccc8 100644
--- a/NDTensors/src/lib/Sectors/src/abstractcategory.jl
+++ b/NDTensors/src/lib/Sectors/src/abstractcategory.jl
@@ -83,9 +83,7 @@ function GradedAxes.fuse_blocklengths(
 end
 
 function GradedAxes.fuse_blocklengths(
-  ::SymmetryStyle,
-  l1::LabelledNumbers.LabelledInteger{<:Integer,<:Sectors.AbstractCategory},
-  l2::LabelledNumbers.LabelledInteger{<:Integer,<:Sectors.AbstractCategory},
+  ::SymmetryStyle, l1::LabelledNumbers.LabelledInteger, l2::LabelledNumbers.LabelledInteger
 )
   fused = LabelledNumbers.label(l1) ⊗ LabelledNumbers.label(l2)
   v =
@@ -96,14 +94,18 @@ function GradedAxes.fuse_blocklengths(
 end
 
 function GradedAxes.fuse_blocklengths(
-  ::AbelianGroup,
-  l1::LabelledNumbers.LabelledInteger{<:Integer,<:Sectors.AbstractCategory},
-  l2::LabelledNumbers.LabelledInteger{<:Integer,<:Sectors.AbstractCategory},
+  ::AbelianGroup, l1::LabelledNumbers.LabelledInteger, l2::LabelledNumbers.LabelledInteger
 )
   fused = LabelledNumbers.label(l1) ⊗ LabelledNumbers.label(l2)
   return LabelledNumbers.labelled(l1 * l2, fused)
 end
 
+function GradedAxes.fuse_blocklengths(
+  ::EmptyCategory, l1::LabelledNumbers.LabelledInteger, l2::LabelledNumbers.LabelledInteger
+)
+  return LabelledNumbers.labelled(l1 * l2, sector())
+end
+
 # cast to range
 to_graded_axis(c::AbstractCategory) = to_graded_axis(LabelledNumbers.labelled(1, c))
 to_graded_axis(l::LabelledNumbers.LabelledInteger) = GradedAxes.gradedrange([l])
diff --git a/NDTensors/src/lib/Sectors/test/test_category_product.jl b/NDTensors/src/lib/Sectors/test/test_category_product.jl
index 8f70741730..772fe524c1 100644
--- a/NDTensors/src/lib/Sectors/test/test_category_product.jl
+++ b/NDTensors/src/lib/Sectors/test/test_category_product.jl
@@ -540,6 +540,9 @@ end
   @test typeof(s) == typeof(sector(()))
   @test typeof(s) == typeof(sector((;)))  # empty NamedTuple is cast to Tuple{}
 
+  g0 = gradedrange([s => 2])
+  @test gradedisequal((@inferred fusion_product(g0, g0)), gradedrange([s => 4]))
+
   @test (@inferred s × U1(1)) == sector(U1(1))
   @test (@inferred s × sector(U1(1))) == sector(U1(1))
   @test (@inferred s × sector(; A=U1(1))) == sector(; A=U1(1))