diff --git a/src/all_building_blocks/wait_blocks.jl b/src/all_building_blocks/wait_blocks.jl
index 004c5fb1cb52c55519436f0d4c6ab415a35d2412..f55383faaf31d5ce86c9e3f374779f01f7b7724b 100644
--- a/src/all_building_blocks/wait_blocks.jl
+++ b/src/all_building_blocks/wait_blocks.jl
@@ -17,7 +17,7 @@ struct Wait <: BaseBuildingBlock
 end
 
 duration(wb::Wait) = wb.duration
-Base.keys(::Wait) = (:empty)
-Base.getindex(wb::Wait) = NoGradient{1}(wb.duration)
+Base.keys(::Wait) = (Val(:empty),)
+Base.getindex(wb::Wait, ::Val{:empty}) = NoGradient{1}(wb.duration)
 
 end
\ No newline at end of file