diff --git a/src/fallbacks.jl b/src/fallbacks.jl
index bdcbfa5..40bb554 100644
--- a/src/fallbacks.jl
+++ b/src/fallbacks.jl
@@ -73,11 +73,11 @@ end
 @inline add!(dest::AbstractVector, val, T, row) = push!(dest, val)
 
 @inline function add_or_widen!(dest::AbstractVector{T}, val::S, nm::Symbol, L, row, len, updated) where {T, S}
-    if S === T || val isa T
+    if S === T || promote_type(S, T) <: T
         add!(dest, val, L, row)
         return dest
     else
-        new = allocatecolumn(Base.promote_typejoin(T, S), max(len, length(dest)))
+        new = allocatecolumn(promote_type(T, S), max(len, length(dest)))
         row > 1 && copyto!(new, 1, dest, 1, row - 1)
         add!(new, val, L, row)
         updated[] = merge(updated[], NamedTuple{(nm,)}((new,)))
diff --git a/src/namedtuples.jl b/src/namedtuples.jl
index b0e947f..a1fedbf 100644
--- a/src/namedtuples.jl
+++ b/src/namedtuples.jl
@@ -40,7 +40,7 @@ function Base.iterate(rows::NamedTupleIterator{Nothing, T}, st=()) where {T}
     x = iterate(rows.x, st...)
     x === nothing && return nothing
     row, st = x
-    names = propertynames(row)
+    names = Tuple(propertynames(row))
     return NamedTuple{names}(Tuple(getproperty(row, nm) for nm in names)), (st,)
 end
 
diff --git a/test/runtests.jl b/test/runtests.jl
index 4363ea7..f1ad220 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -97,7 +97,11 @@ end
     @test length(rt2) == 9
 
     rt = [(a=1, b=4.0, c="7"), (a=2.0, b=missing, c="8"), (a=3, b=6.0, c="9")]
-    @test isequal(Tables.buildcolumns(nothing, rt), (a = Real[1, 2.0, 3], b = Union{Missing, Float64}[4.0, missing, 6.0], c = ["7", "8", "9"]))
+    tt = Tables.buildcolumns(nothing, rt)
+    @test isequal(tt, (a = [1.0, 2.0, 3.0], b = Union{Missing, Float64}[4.0, missing, 6.0], c = ["7", "8", "9"]))
+    @test tt.a[1] === 1.0
+    @test tt.a[2] === 2.0
+    @test tt.a[3] === 3.0
 
     nti = Tables.NamedTupleIterator{Nothing, typeof(rt)}(rt)
     nti2 = collect(nti)