diff --git a/examples/quaternion.jl b/examples/quaternion.jl
index 536e047c615e8..f2efb4336afa2 100644
--- a/examples/quaternion.jl
+++ b/examples/quaternion.jl
@@ -7,6 +7,11 @@ immutable Quaternion{T<:Real} <: Number
     q3::T
 end
 
+function Quaternion{A<:Real,B<:Real,C<:Real,D<:Real}(q0::A,q1::B,q2::C,q3::D)
+  T = promote_type(A,B,C,D)
+  Quaternion{T}(convert(T,q0), convert(T,q1), convert(T,q2), convert(T,q3))
+end
+
 convert{T}(::Type{Quaternion{T}}, x::Real) =
     Quaternion(convert(T,x), convert(T,0), convert(T,0), convert(T,0))
 
@@ -22,6 +27,8 @@ promote_rule{T,S}(::Type{Complex{T}}, ::Type{Quaternion{S}}) =
 promote_rule{S}(::Type{Bool}, ::Type{Quaternion{S}}) = Quaternion{S}
 promote_rule{T<:Real,S}(::Type{T}, ::Type{Quaternion{S}}) =
     Quaternion{promote_type(T,S)}
+promote_rule{T,S}(::Type{Quaternion{T}}, ::Type{Quaternion{S}}) =
+    Quaternion{promote_type(T,S)}
 
 function show(io::IO, z::Quaternion)
     show(io, z.q0)