diff --git a/Project.toml b/Project.toml
index 6725fb41..85a272e8 100644
--- a/Project.toml
+++ b/Project.toml
@@ -23,7 +23,7 @@ DataFrames = "0.21, 0.22, 1"
 DelimitedFiles = "1"
 DocStringExtensions = "0.8, 0.9"
 HiGHS = "1.4"
-IntervalArithmetic = "0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20"
+IntervalArithmetic = "0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21"
 JuMP = "0.21.4, 0.21.5, 0.22, 0.23, 1"
 MAT = "0.5, 0.6, 0.7, 0.8, 0.9, 0.10"
 MathOptInterface = "0.9, 0.10, 1"
diff --git a/src/vendor/ConditionalJuMP.jl b/src/vendor/ConditionalJuMP.jl
index 6fccbecf..68e3d6db 100644
--- a/src/vendor/ConditionalJuMP.jl
+++ b/src/vendor/ConditionalJuMP.jl
@@ -1,5 +1,5 @@
 using JuMP
-using IntervalArithmetic: Interval
+using IntervalArithmetic
 
 # We vendor ConditionalJuMP (https://github.com/rdeits/ConditionalJuMP.jl/blob/e0c406077c0b07be76e02f72c3a7a7aa650df82f/src/ConditionalJuMP.jl)
 # so that we can use JuMP >= 0.2.0
@@ -23,12 +23,15 @@ function owner_model(
     return nothing
 end
 
-interval(x::Number) = Interval(x, x)
-interval(x::JuMP.VariableRef) = Interval(lower_bound(x), upper_bound(x))
-function interval(e::JuMP.GenericAffExpr)
-    result = Interval(e.constant, e.constant)
+# Supplements constructors in https://github.com/JuliaIntervals/IntervalArithmetic.jl/blob/master/src/intervals/construction.jl.
+IntervalArithmetic.interval(x::JuMP.VariableRef) =
+    IntervalArithmetic.interval(lower_bound(x), upper_bound(x))
+function IntervalArithmetic.interval(e::JuMP.GenericAffExpr)
+    result = IntervalArithmetic.interval(e.constant)
     for (var, coef) in e.terms
-        result += Interval(coef, coef) * Interval(lower_bound(var), upper_bound(var))
+        result +=
+            IntervalArithmetic.interval(coef) *
+            IntervalArithmetic.interval(lower_bound(var), upper_bound(var))
     end
     return result
 end
@@ -37,7 +40,7 @@ lower_bound(x::Number) = x
 upper_bound(x::Number) = x
 lower_bound(x::JuMP.VariableRef) = JuMP.lower_bound(x)
 upper_bound(x::JuMP.VariableRef) = JuMP.upper_bound(x)
-lower_bound(e::JuMP.GenericAffExpr) = lower_bound(interval(e))
-upper_bound(e::JuMP.GenericAffExpr) = upper_bound(interval(e))
+lower_bound(e::JuMP.GenericAffExpr) = lower_bound(IntervalArithmetic.interval(e))
+upper_bound(e::JuMP.GenericAffExpr) = upper_bound(IntervalArithmetic.interval(e))
 lower_bound(i::Interval) = i.lo
 upper_bound(i::Interval) = i.hi
diff --git a/test/vendor/ConditionalJuMP.jl b/test/vendor/ConditionalJuMP.jl
index 14c0439f..da6fcefc 100644
--- a/test/vendor/ConditionalJuMP.jl
+++ b/test/vendor/ConditionalJuMP.jl
@@ -1,7 +1,8 @@
 using Test
 
 using JuMP
-using MIPVerify: owner_model, interval, lower_bound, upper_bound
+using IntervalArithmetic
+using MIPVerify: owner_model, lower_bound, upper_bound
 @isdefined(TestHelpers) || include("../TestHelpers.jl")
 
 TestHelpers.@timed_testset "ConditionalJuMP.jl" begin
@@ -23,7 +24,7 @@ TestHelpers.@timed_testset "ConditionalJuMP.jl" begin
         e = 2 * x + 1
 
         @testset "Number" begin
-            i = interval(5.0)
+            i = IntervalArithmetic.interval(5.0)
             @test lower_bound(i) == 5.0
             @test upper_bound(i) == 5.0
         end
@@ -32,7 +33,7 @@ TestHelpers.@timed_testset "ConditionalJuMP.jl" begin
             @test lower_bound(x) == 1
             @test upper_bound(x) == 3
 
-            i = interval(x)
+            i = IntervalArithmetic.interval(x)
             @test lower_bound(i) == 1
             @test upper_bound(i) == 3
         end
@@ -50,13 +51,13 @@ TestHelpers.@timed_testset "ConditionalJuMP.jl" begin
             @test lower_bound(AffExpr(2)) == 2
             @test upper_bound(AffExpr(2)) == 2
 
-            i = interval(e)
+            i = IntervalArithmetic.interval(e)
             @test lower_bound(i) == lower_bound(e)
             @test upper_bound(i) == upper_bound(e)
         end
 
         @testset "Interval" begin
-            i = interval(5.0)
+            i = IntervalArithmetic.interval(5.0)
             @test lower_bound(i) == 5.0
             @test upper_bound(i) == 5.0
         end