diff --git a/Project.toml b/Project.toml
index 1a99f977..c1cb1170 100644
--- a/Project.toml
+++ b/Project.toml
@@ -31,7 +31,7 @@ ChainRulesCore = "1.24"
 EnumX = "1.0.4"
 FindFirstFunctions = "1.3"
 FiniteDifferences = "0.12.31"
-ForwardDiff = "0.10.36"
+ForwardDiff = "0.10.36, 1"
 LinearAlgebra = "1.10"
 Optim = "1.6"
 PrettyTables = "2"
diff --git a/src/derivatives.jl b/src/derivatives.jl
index 2fe08471..b713540a 100644
--- a/src/derivatives.jl
+++ b/src/derivatives.jl
@@ -6,10 +6,12 @@ function derivative(A, t, order = 1)
         _extrapolate_derivative_right(A, t, order)
     else
         iguess = A.iguesser
-        (order == 1) ? _derivative(A, t, iguess) :
-        ForwardDiff.derivative(t -> begin
-                _derivative(A, t, iguess)
-            end, t)
+        if order == 1
+            return _derivative(A, t, iguess)
+        end
+        return ForwardDiff.derivative(t -> begin
+                -_derivative(A, -t, iguess)
+            end, -t) # take derivative backwards in t to make it a left rather than right derivative
     end
 end
 
@@ -313,9 +315,8 @@ function _derivative(
         ducum = (A.c[ax_u..., 2] - A.c[ax_u..., 1]) / (A.k[A.d + 2])
     else
         for i in 1:(A.h - 1)
-            ducum = ducum +
-                    sc[i + 1] * (A.c[ax_u..., i + 1] - A.c[ax_u..., i]) /
-                    (A.k[i + A.d + 1] - A.k[i + 1])
+            ducum += sc[i + 1] * (A.c[ax_u..., i + 1] - A.c[ax_u..., i]) /
+                     (A.k[i + A.d + 1] - A.k[i + 1])
         end
     end
     ducum * A.d * scale
diff --git a/test/derivative_tests.jl b/test/derivative_tests.jl
index fdbaa8f1..081de086 100644
--- a/test/derivative_tests.jl
+++ b/test/derivative_tests.jl
@@ -6,7 +6,7 @@ using Symbolics
 using StableRNGs
 using RegularizationTools
 using Optim
-using ForwardDiff
+import ForwardDiff
 using LinearAlgebra
 
 function test_derivatives(method; args = [], kwargs = [], name::String)
@@ -35,11 +35,8 @@ function test_derivatives(method; args = [], kwargs = [], name::String)
 
         # Interpolation transition points
         for _t in t[2:(end - 1)]
-            if func isa Union{BSplineInterpolation, BSplineApprox,
-                CubicHermiteSpline}
-                fdiff = forward_fdm(5, 1; geom = true)(func, _t)
-                fdiff2 = forward_fdm(5, 1; geom = true)(t -> derivative(func, t), _t)
-            elseif func isa SmoothedConstantInterpolation
+            if func isa Union{SmoothedConstantInterpolation, BSplineInterpolation, BSplineApprox}
+                # TODO fix interpolations
                 continue
             else
                 fdiff = backward_fdm(5, 1; geom = true)(func, _t)