diff --git a/src/wait.jl b/src/wait.jl
index c3b4a687342f70c2a5e7c9307f2d21206b7ebcf1..652225a1016760de93ce87cc383a58fe8459e6a1 100644
--- a/src/wait.jl
+++ b/src/wait.jl
@@ -19,6 +19,9 @@ Duration can be set to one of:
 struct WaitBlock <: BuildingBlock
     duration :: VariableType
     function WaitBlock(duration=nothing)
+        if duration isa Number
+            return new(duration)
+        end
         res = new(
             get_free_variable(duration),
         )