diff --git a/base/mathconstants.jl b/base/mathconstants.jl
index de6b98cea634d..d26f5115b5ccb 100644
--- a/base/mathconstants.jl
+++ b/base/mathconstants.jl
@@ -29,7 +29,7 @@ end
 Base.@assume_effects :foldable function (::Type{T})(x::_KnownIrrational, r::RoundingMode) where {T<:Union{Float32,Float64}}
     Base._irrational_to_float(T, x, r)
 end
-Base.@assume_effects :foldable function rationalize(::Type{T}, x::_KnownIrrational; tol::Real=0) where {T<:Integer}
+Base.@assume_effects :foldable function Base.rationalize(::Type{T}, x::_KnownIrrational; tol::Real=0) where {T<:Integer}
     Base._rationalize_irrational(T, x, tol)
 end
 Base.@assume_effects :foldable function Base.lessrational(rx::Rational, x::_KnownIrrational)