diff --git a/src/domains/trivial.jl b/src/domains/trivial.jl
index 7bfbe19..3243540 100644
--- a/src/domains/trivial.jl
+++ b/src/domains/trivial.jl
@@ -5,7 +5,7 @@
 struct EmptySpace{T} <: Domain{T}
 end
 
-EmptySet = EmptySpace
+const EmptySet = EmptySpace
 
 const AnyEmptySpace = EmptySpace{Any}
 
diff --git a/src/generic/interface.jl b/src/generic/interface.jl
index ffa1037..020c687 100644
--- a/src/generic/interface.jl
+++ b/src/generic/interface.jl
@@ -66,7 +66,7 @@ DomainStyle(::Type{<:Number}) = IsDomain()
 DomainStyle(::Type{<:AbstractSet}) = IsDomain()
 DomainStyle(::Type{<:AbstractArray}) = IsDomain()
 
-BaseDomainType = Union{<:Number,<:AbstractSet,<:AbstractArray}
+const BaseDomainType = Union{<:Number,<:AbstractSet,<:AbstractArray}
 
 """
     domain(d)
diff --git a/src/generic/productdomain.jl b/src/generic/productdomain.jl
index 3dea2d0..303d2e1 100644
--- a/src/generic/productdomain.jl
+++ b/src/generic/productdomain.jl
@@ -57,8 +57,8 @@ closure(d::ProductDomain) = ProductDomain(map(closure, components(d)))
 
 center(d::ProductDomain) = toexternalpoint(d, map(center, components(d)))
 
-VcatDomainElement = Union{Domain{<:Number},EuclideanDomain}
-VcatEltype = Union{Type{<:Number},Type{<:StaticVector}}
+const VcatDomainElement = Union{Domain{<:Number},EuclideanDomain}
+const VcatEltype = Union{Type{<:Number},Type{<:StaticVector}}
 
 """
 	ProductDomain(domains...)
@@ -133,7 +133,7 @@ Alias for [`cartesianproduct`](@ref). Note that this differs from LinearAlgebra.
 !!! note
 	`×` requires at least v0.8.0 of DomainSets.jl.
 """
-× = cartesianproduct
+const × = cartesianproduct
 
 Base.:^(d::Domain, n::Int) = productdomain(ntuple(i->d, n)...)