diff --git a/src/difference.jl b/src/difference.jl
index 4c5ee160c..1d741afcb 100644
--- a/src/difference.jl
+++ b/src/difference.jl
@@ -38,4 +38,4 @@ Base.nameof(::Difference) = :Difference
 function Base.:(==)(D1::Difference, D2::Difference)
     return isequal(D1.t, D2.t) && isequal(D1.dt, D2.dt) && isequal(D1.update, D2.update)
 end
-Base.hash(D::Difference, u::UInt) = hash(D.dt, hash(D.t, xor(u, 0x055640d6d952f101)))
+Base.hash(D::Difference, u::UInt) = hash(D.dt, hash(D.t, xor(u, 0x055640d6d952f101 % UInt)))
diff --git a/src/utils/utils.jl b/src/utils/utils.jl
index 10a684407..52d898ec0 100644
--- a/src/utils/utils.jl
+++ b/src/utils/utils.jl
@@ -3,7 +3,7 @@
 # Values is 4/sqrt(3)", http://arxiv.org/abs/1305.5870
 # Code taken from https://github.com/erichson/optht
 
-function optimal_svht(m::Int64, n::Int64; known_noise::Bool = false)
+function optimal_svht(m::Integer, n::Integer; known_noise::Bool = false)
     @assert m / n > 0
     @assert m / n <= 1
 
diff --git a/test/Core/implicit_basis.jl b/test/Core/implicit_basis.jl
index 09c301b00..64911a2a8 100644
--- a/test/Core/implicit_basis.jl
+++ b/test/Core/implicit_basis.jl
@@ -56,6 +56,8 @@ end
     discrete_prob = DiscreteDataDrivenProblem(x)
 
     d = Difference(get_iv(basis), dt = 1.0)
+    # hash(::Difference, ::UInt) must return the platform native UInt.
+    @test typeof(hash(d, UInt(1))) === UInt
     @test Symbolics.symtype(d(first(states(basis)))) === Real
     @test isempty(Symbolics.shape(d(first(states(basis)))))
     ∂ = Differential(get_iv(basis))
diff --git a/test/Core/utils.jl b/test/Core/utils.jl
index b22600f8a..b6b81c117 100644
--- a/test/Core/utils.jl
+++ b/test/Core/utils.jl
@@ -18,6 +18,8 @@ using LinearAlgebra
 end
 
 @testset "Optimal Shrinkage" begin
+    # Callers pass size(...) extents; Int32 must be accepted on every platform.
+    @test DataDrivenDiffEq.optimal_svht(Int32(10), Int32(20)) isa Real
     t = collect(-2:0.01:2)
     U = [cos.(t) .* exp.(-t .^ 2) sin.(2 * t)]
     S = Diagonal([2.0; 3.0])