diff --git a/.github/workflows/CompatHelper.yml b/.github/workflows/CompatHelper.yml
index 3e6ff906..8388ff56 100644
--- a/.github/workflows/CompatHelper.yml
+++ b/.github/workflows/CompatHelper.yml
@@ -23,7 +23,7 @@ jobs:
       - name: Run CompatHelper
         run: |
           julia -e 'import CompatHelper;
-            CompatHelper.main(; subdirs=["", "test", "docs"],
+            CompatHelper.main(; subdirs=["", "test", "docs", "test/IntervalArithmetic v0.22"],
             bump_compat_containing_equality_specifier=false)'
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/Project.toml b/Project.toml
index 5b1f2792..2bd62bd7 100644
--- a/Project.toml
+++ b/Project.toml
@@ -6,13 +6,15 @@ version = "0.2.6"
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 IntervalArithmetic = "d1acc4aa-44c8-5952-acd4-ba5d80a2a253"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+PkgVersion = "eebad327-c553-4316-9ea0-9fa01ccd7688"
 ReachabilityBase = "379f33d0-9447-4353-bd03-d664070e549f"
 Requires = "ae029012-a4dd-5104-9daa-d747884805df"
 
 [compat]
 ForwardDiff = "0.10"
-IntervalArithmetic = "0.15 - 0.20, =0.21.0"  # v0.21.1 removed IntervalBox
+IntervalArithmetic = "0.15 - 0.22"
 LinearAlgebra = "<0.0.1, 1.6"
+PkgVersion = "0.3"
 ReachabilityBase = "0.1.1 - 0.3"
 Requires = "0.5, 1"
 julia = "1.6"
diff --git a/src/RangeEnclosures.jl b/src/RangeEnclosures.jl
index cd72be66..18522e85 100644
--- a/src/RangeEnclosures.jl
+++ b/src/RangeEnclosures.jl
@@ -3,11 +3,30 @@ module RangeEnclosures
 using Requires
 import ForwardDiff
 using LinearAlgebra: dot
-using IntervalArithmetic: Interval, IntervalBox, interval, inf, sup, mid,
-                          emptyinterval, hull, diam, bisect, (..)
-const Interval_or_IntervalBox = Union{Interval,IntervalBox}
+import IntervalArithmetic
+using IntervalArithmetic: Interval, interval, inf, sup, mid,
+                          emptyinterval, hull, diam, bisect
 using ReachabilityBase.Require
 
+# resolving IntervalArithmetic version problems
+import PkgVersion
+@static if VERSION >= v"1.9"
+    vIA = pkgversion(IntervalArithmetic)
+else
+    vIA = PkgVersion.Version(IntervalArithmetic)
+end
+@static if vIA < v"0.22"
+    using IntervalArithmetic: (..)
+else
+    .. = interval
+end
+@static if vIA < v"0.21.1"
+    using IntervalArithmetic: IntervalBox
+else
+    IntervalBox = AbstractVector{<:Interval}
+end
+const Interval_or_IntervalBox = Union{Interval,IntervalBox}
+
 include("algorithms.jl")
 include("intervalarithmetic.jl")
 include("branchandbound.jl")
diff --git a/src/branchandbound.jl b/src/branchandbound.jl
index 5baf54fd..143f7b02 100644
--- a/src/branchandbound.jl
+++ b/src/branchandbound.jl
@@ -30,8 +30,8 @@ end
 
 function _monotonicity_check(f::Function, X::Interval, dfX::Interval)
     if inf(dfX) >= 0 || sup(dfX) <= 0  # monotone function, evaluate at extrema
-        lo = interval(X.lo)
-        hi = interval(X.hi)
+        lo = interval(inf(X))
+        hi = interval(sup(X))
         return hull(f(lo), f(hi)), true
     end
 
diff --git a/test/IntervalArithmetic v0.22/Project.toml b/test/IntervalArithmetic v0.22/Project.toml
new file mode 100644
index 00000000..c02da25a
--- /dev/null
+++ b/test/IntervalArithmetic v0.22/Project.toml	
@@ -0,0 +1,17 @@
+[deps]
+Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
+Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+DynamicPolynomials = "7c1d4256-1411-5781-91ec-d7bc3513ac07"
+IntervalArithmetic = "d1acc4aa-44c8-5952-acd4-ba5d80a2a253"
+RangeEnclosures = "1b4d18b6-9e5d-11e9-236c-f792b01831f8"
+SDPA = "b9a10b5b-afa4-512f-a053-bb3d8080febc"
+SumOfSquares = "4b9e565b-77fc-50a5-a571-1244f986bda1"
+Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+
+[compat]
+Aqua = "0.8.9"
+Documenter = "0.27, 1"
+DynamicPolynomials = "0.3 - 0.6"
+IntervalArithmetic = "0.22"
+SDPA = "0.2 - 0.6"
+SumOfSquares = "0.3.6 - 0.7"
diff --git a/test/IntervalArithmetic v0.22/runtests.jl b/test/IntervalArithmetic v0.22/runtests.jl
new file mode 100644
index 00000000..2fb52826
--- /dev/null
+++ b/test/IntervalArithmetic v0.22/runtests.jl	
@@ -0,0 +1,3 @@
+global oldIA = false
+
+include("../runtests.jl")
diff --git a/test/paper.jl b/test/paper.jl
index c0e5ac31..4aecbcc5 100644
--- a/test/paper.jl
+++ b/test/paper.jl
@@ -10,34 +10,40 @@ struct MyEnclosure end
     end
 
     f(x) = x
-    @test enclose(f, 0 .. 1, MyEnclosure()) == 1 .. 2
+    @test isequal_interval(enclose(f, 0 .. 1, MyEnclosure()), 1 .. 2)
 end
 
 @testset "How to use the package" begin
     f(x) = -sum(k * x * sin(k * (x - 3) / 3) for k in 1:5)
     D = -10 .. 10
-    @test enclose(f, D, NaturalEnclosure()) == interval(-150, 150)
+    @test isequal_interval(enclose(f, D, NaturalEnclosure()), interval(-150, 150))
     res = enclose(f, D, BranchAndBoundEnclosure())
-    @test res isa Interval && inf(res) ≈ -56.42311 && sup(res) ≈ 34.99878
+    @test res isa Interval
+    if oldIA
+        @test inf(res) ≈ -56.42311 && sup(res) ≈ 34.99878
+    else
+        @test inf(res) ≈ -56.42400 && sup(res) ≈ 34.988386
+    end
 end
 
 @testset "Combining different solvers" begin
     g(x) = x^2 - 2 * x + 1
     Dg = 0 .. 4
-    @test enclose(g, Dg, NaturalEnclosure()) == interval(-7, 17)
-    @test enclose(g, Dg, MeanValueEnclosure()) == interval(-11, 13)
+    @test isequal_interval(enclose(g, Dg, NaturalEnclosure()), interval(-7, 17))
+    @test isequal_interval(enclose(g, Dg, MeanValueEnclosure()), interval(-11, 13))
 
-    @test enclose(g, Dg, [NaturalEnclosure(), MeanValueEnclosure()]) == interval(-7, 13)
+    # TODO combining solvers is currently not supported for IntervalArithmetic v0.22
+    @ts @test isequal_interval(enclose(g, Dg, [NaturalEnclosure(), MeanValueEnclosure()]), interval(-7, 13))
 end
 
-@testset "Using solvers based on external libraries" begin
+@ts @testset "Using solvers based on external libraries" begin
     g(x) = x^2 - 2 * x + 1
     Dg = 0 .. 4
     res = enclose(g, Dg, MooreSkelboeEnclosure())
     @test res isa Interval && inf(res) ≈ -0.0019195181 && sup(res) ≈ 9.0010805
 end
 
-@testset "Multivariate functions" begin
+@ts @testset "Multivariate functions" begin
     h(x) = sin(x[1]) - cos(x[2]) - sin(x[1]) * cos(x[1])
     Dh = IntervalBox(-5 .. 5, -5 .. 5)
     res = enclose(h, Dh, BranchAndBoundEnclosure())
diff --git a/test/runtests.jl b/test/runtests.jl
index dab2a22d..df1c9b71 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,22 +1,51 @@
 using Test, RangeEnclosures
-using AffineArithmetic, IntervalOptimisation, TaylorModels, SDPA, SumOfSquares
+using SDPA, SumOfSquares
 using DynamicPolynomials: @polyvar
 
-available_solvers = (NaturalEnclosure(),
-                     MeanValueEnclosure(),
-                     AffineArithmeticEnclosure(),
-                     MooreSkelboeEnclosure(),
-                     TaylorModelsEnclosure(),
-                     BranchAndBoundEnclosure())
+global oldIA
+if !isdefined(Main, :oldIA)
+    @show oldIA = true
+end
+
+@static if oldIA
+    using AffineArithmetic, IntervalOptimisation, TaylorModels
+    available_solvers = (NaturalEnclosure(),
+                         MeanValueEnclosure(),
+                         AffineArithmeticEnclosure(),
+                         MooreSkelboeEnclosure(),
+                         TaylorModelsEnclosure(),
+                         BranchAndBoundEnclosure())
+
+    # execute the argument code
+    macro ts(arg)
+        quote
+            $(esc(arg))
+        end
+    end
+
+    isequal_interval = (==)
+else
+    available_solvers = (NaturalEnclosure(),
+                         MeanValueEnclosure(),
+                         BranchAndBoundEnclosure())
+
+    # skip the argument code
+    macro ts(arg) end
+
+    using RangeEnclosures: Interval  # this is necessary for some reason
+    using RangeEnclosures.IntervalArithmetic: isequal_interval, inf, sup
+end
 
 include("univariate.jl")
-include("multivariate.jl")
+@ts include("multivariate.jl")
 include("paper.jl")
 
-using Documenter
-include("../docs/init.jl")
-@testset "doctests" begin
-    doctest(RangeEnclosures)
+@ts begin
+    using Documenter
+    include("../docs/init.jl")
+    @testset "doctests" begin
+        doctest(RangeEnclosures)
+    end
 end
 
 include("Aqua.jl")
diff --git a/test/univariate.jl b/test/univariate.jl
index 9ab07ef2..e964b65e 100644
--- a/test/univariate.jl
+++ b/test/univariate.jl
@@ -29,15 +29,17 @@ end
     rleft, rright = relative_precision(x, xref)
     @test rleft ≤ 1e-5 && rright ≤ 1e-5
 
-    x = enclose(f, dom, TaylorModelsEnclosure(; order=4))
-    xref = interval(-4.2783, 12.7084)
-    rleft, rright = relative_precision(x, xref)
-    @test rleft ≤ 1e-5 && rright ≤ 1e-5
+    @ts begin
+        x = enclose(f, dom, TaylorModelsEnclosure(; order=4))
+        xref = interval(-4.2783, 12.7084)
+        rleft, rright = relative_precision(x, xref)
+        @test rleft ≤ 1e-5 && rright ≤ 1e-5
 
-    x = enclose(f, dom, MooreSkelboeEnclosure())
-    xref = interval(4.83299, 10.5448)
-    rleft, rright = relative_precision(x, xref)
-    @test rleft ≤ 1e-5 && rright ≤ 1e-5
+        x = enclose(f, dom, MooreSkelboeEnclosure())
+        xref = interval(4.83299, 10.5448)
+        rleft, rright = relative_precision(x, xref)
+        @test rleft ≤ 1e-5 && rright ≤ 1e-5
+    end
 end
 
 @testset "Test univariate polynomial input" begin
@@ -56,7 +58,7 @@ end
     @test rleft ≤ 1e-5 && rright ≤ 1e-5
 end
 
-@testset "Taylor-model solver without normalization" begin
+@ts @testset "Taylor-model solver without normalization" begin
     f(x) = x^2 - 5x
     dom = interval(-1, 1)
     x = enclose(f, dom, TaylorModelsEnclosure(; normalize=false))