diff --git a/docs/src/3-mixed-integer-optimization.jl b/docs/src/3-mixed-integer-optimization.jl
index e51d569..b29d909 100644
--- a/docs/src/3-mixed-integer-optimization.jl
+++ b/docs/src/3-mixed-integer-optimization.jl
@@ -31,8 +31,7 @@ IntegerFromTo(1, 6)
 
 # ...and include this bound in constraints and variables:
 
-dice_system =
-    C.variables(keys = [:first_dice, :second_dice], bounds = [IntegerFromTo(1, 6)])
+dice_system = C.variables(keys = [:first_dice, :second_dice], bounds = IntegerFromTo(1, 6))
 
 # Now the main thing that is left is to be able to translate this bound to JuMP
 # for solving. We can slightly generalize our constraint-translation system
@@ -103,7 +102,7 @@ dices_thrown = C.constraint_values(
 # Let's find the size of the smallest right-angled triangle with integer side
 # sizes (aka a Pythagorean triple).
 
-vars = C.variables(keys = [:a, :b, :c], bounds = (IntegerFromTo(1, 100),))
+vars = C.variables(keys = [:a, :b, :c], bounds = IntegerFromTo(1, 100))
 
 # For simpliclty, we make a shortcut for "values" in all variables:
 v = C.tree_map(vars, C.value, C.Value)
diff --git a/src/constraint_tree.jl b/src/constraint_tree.jl
index f2c627a..ff6d27d 100644
--- a/src/constraint_tree.jl
+++ b/src/constraint_tree.jl
@@ -194,7 +194,7 @@ maximum))`, which has the correct length.
 function variables(; keys::AbstractVector{Symbol}, bounds = nothing)
     bs =
         isnothing(bounds) ? Base.Iterators.cycle(tuple(nothing)) :
-        length(bounds) == 1 ? Base.Iterators.cycle(bounds) :
+        typeof(bounds) <: Bound ? Base.Iterators.cycle(tuple(bounds)) :
         length(bounds) == length(keys) ? bounds :
         error("lengths of bounds and keys differ for allocated variables")
     ConstraintTree(