diff --git a/lib/OrdinaryDiffEqCore/src/caches/basic_caches.jl b/lib/OrdinaryDiffEqCore/src/caches/basic_caches.jl
index f836d61b9b..72f9a6cdfd 100644
--- a/lib/OrdinaryDiffEqCore/src/caches/basic_caches.jl
+++ b/lib/OrdinaryDiffEqCore/src/caches/basic_caches.jl
@@ -73,7 +73,8 @@ function alg_cache(alg::CompositeAlgorithm{CS, Tuple{A1, A2, A3, A4, A5, A6}}, u
     args = (u, rate_prototype, uEltypeNoUnits,
         uBottomEltypeNoUnits, tTypeNoUnits, uprev, uprev2, f, t, dt,
         reltol, p, calck, Val(V))
-    argT = map(typeof, args)
+    # Core.Typeof to turn uEltypeNoUnits into Type{uEltypeNoUnits} rather than DataType
+    argT = map(Core.Typeof, args)
     T1 = Base.promote_op(alg_cache, A1, argT...)
     T2 = Base.promote_op(alg_cache, A2, argT...)
     T3 = Base.promote_op(alg_cache, A3, argT...)
diff --git a/lib/OrdinaryDiffEqCore/src/dense/generic_dense.jl b/lib/OrdinaryDiffEqCore/src/dense/generic_dense.jl
index f8dfa068e2..9978478560 100644
--- a/lib/OrdinaryDiffEqCore/src/dense/generic_dense.jl
+++ b/lib/OrdinaryDiffEqCore/src/dense/generic_dense.jl
@@ -168,10 +168,12 @@ function default_ode_interpolant(
         return ode_interpolant(Θ, integrator.dt, integrator.uprev,
             integrator.u, integrator.k, cache.cache5, idxs,
             deriv, integrator.differential_vars)
-    else # alg_choice == 6
+    elseif alg_choice == 6
         return ode_interpolant(Θ, integrator.dt, integrator.uprev,
             integrator.u, integrator.k, cache.cache6, idxs,
             deriv, integrator.differential_vars)
+    else
+        error("DefaultCache invalid alg_choice. File an issue.")
     end
 end
 
@@ -227,6 +229,8 @@ end
             ode_interpolant!(val, Θ, integrator.dt, integrator.uprev, integrator.u,
                 integrator.k, integrator.cache.cache6,
                 idxs, deriv, integrator.differential_vars)
+        else
+            error("DefaultCache invalid alg_choice. File an issue.")
         end
     else
         ode_interpolant!(val, Θ, integrator.dt, integrator.uprev, integrator.u,
@@ -256,10 +260,12 @@ function default_ode_interpolant!(
         return ode_interpolant!(val, Θ, integrator.dt, integrator.uprev,
             integrator.u, integrator.k, cache.cache5, idxs,
             deriv, integrator.differential_vars)
-    else # alg_choice == 6
+    elseif alg_choice == 6
         return ode_interpolant!(val, Θ, integrator.dt, integrator.uprev,
             integrator.u, integrator.k, cache.cache6, idxs,
             deriv, integrator.differential_vars)
+    else
+        error("DefaultCache invalid alg_choice. File an issue.")
     end
 end
 
@@ -380,6 +386,8 @@ function default_ode_extrapolant!(
         ode_interpolant!(val, Θ, integrator.t - integrator.tprev,
             integrator.uprev2, integrator.uprev,
             integrator.k, cache.cache6, idxs, deriv, integrator.differential_vars)
+    else
+        error("DefaultCache invalid alg_choice. File an issue.")
     end
 end
 
@@ -444,6 +452,8 @@ function default_ode_extrapolant(
         ode_interpolant(Θ, integrator.t - integrator.tprev,
             integrator.uprev2, integrator.uprev,
             integrator.k, cache.cache6, idxs, deriv, integrator.differential_vars)
+    else
+        error("DefaultCache invalid alg_choice. File an issue.")
     end
 end
 
@@ -810,6 +820,8 @@ function ode_interpolation(tval::Number, id::I, idxs, deriv::D, p,
                     cache.cache6) # update the kcurrent
                 val = ode_interpolant(Θ, dt, timeseries[i₋], timeseries[i₊], ks[i₊],
                     cache.cache6, idxs, deriv, differential_vars)
+            else
+                error("DefaultCache invalid alg_choice. File an issue.")
             end
         else
             _ode_addsteps!(ks[i₊], ts[i₋], timeseries[i₋], timeseries[i₊], dt, f, p,
@@ -892,6 +904,8 @@ function ode_interpolation!(out, tval::Number, id::I, idxs, deriv::D, p,
                     cache.cache6) # update the kcurrent
                 ode_interpolant!(out, Θ, dt, timeseries[i₋], timeseries[i₊], ks[i₊],
                     cache.cache6, idxs, deriv, differential_vars)
+            else
+                error("DefaultCache invalid alg_choice. File an issue.")
             end
         else
             _ode_addsteps!(ks[i₊], ts[i₋], timeseries[i₋], timeseries[i₊], dt, f, p,
diff --git a/lib/OrdinaryDiffEqDefault/test/default_solver_tests.jl b/lib/OrdinaryDiffEqDefault/test/default_solver_tests.jl
index 8676b4a57a..c434bc80ab 100644
--- a/lib/OrdinaryDiffEqDefault/test/default_solver_tests.jl
+++ b/lib/OrdinaryDiffEqDefault/test/default_solver_tests.jl
@@ -40,6 +40,8 @@ end
 prob_rober = ODEProblem(rober, [1.0, 0.0, 0.0], (0.0, 1e3), (0.04, 3e7, 1e4))
 sol = solve(prob_rober)
 rosensol = solve(prob_rober, AutoTsit5(Rosenbrock23(autodiff = false)))
+#test that cache is type stable
+@test typeof(sol.interp.cache.cache3) == typeof(rosensol.interp.cache.caches[2])
 # test that default has the same performance as AutoTsit5(Rosenbrock23()) (which we expect it to use for this).
 @test sol.stats.naccept == rosensol.stats.naccept
 @test sol.stats.nf == rosensol.stats.nf
@@ -50,6 +52,8 @@ rosensol = solve(prob_rober, AutoTsit5(Rosenbrock23(autodiff = false)))
 sol = solve(prob_rober, reltol = 1e-7, abstol = 1e-7)
 rosensol = solve(
     prob_rober, AutoVern7(Rodas5P(autodiff = false)), reltol = 1e-7, abstol = 1e-7)
+#test that cache is type stable
+@test typeof(sol.interp.cache.cache4) == typeof(rosensol.interp.cache.caches[2])
 # test that default has the same performance as AutoTsit5(Rosenbrock23()) (which we expect it to use for this).
 @test sol.stats.naccept == rosensol.stats.naccept
 @test sol.stats.nf == rosensol.stats.nf