diff --git a/base/reducedim.jl b/base/reducedim.jl
index c473049dd5fa0..ab62a39190926 100644
--- a/base/reducedim.jl
+++ b/base/reducedim.jl
@@ -321,8 +321,10 @@ julia> mapreduce(isodd, |, a, dims=1)
 """
 mapreduce(f, op, A::AbstractArrayOrBroadcasted; dims=:, init=_InitialValue()) =
     _mapreduce_dim(f, op, init, A, dims)
-mapreduce(f, op, A::AbstractArrayOrBroadcasted...; kw...) =
-    reduce(op, map(f, A...); kw...)
+function mapreduce(f, op, A::AbstractArrayOrBroadcasted...; kw...)
+    get(kw, :dims, :) === (:) && return mapreduce(A -> f(A...), op, zip(A...); kw...)
+    return reduce(op, map(f, A...); kw...)
+end
 
 _mapreduce_dim(f, op, nt, A::AbstractArrayOrBroadcasted, ::Colon) =
     mapfoldl_impl(f, op, nt, A)