diff --git a/src/utils.jl b/src/utils.jl
index 2a1508075..2e5e3b2ad 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -1,12 +1,3 @@
-struct NullCallback end
-(x::NullCallback)(args...) = false;
-const DEFAULT_CALLBACK = NullCallback()
-
-struct NullData end
-const DEFAULT_DATA = Iterators.cycle((NullData(),))
-Base.iterate(::NullData, i = 1) = nothing
-Base.length(::NullData) = 0
-
 function get_maxiters(data)
     Iterators.IteratorSize(typeof(DEFAULT_DATA)) isa Iterators.IsInfinite ||
         Iterators.IteratorSize(typeof(DEFAULT_DATA)) isa Iterators.SizeUnknown ?