diff --git a/Project.toml b/Project.toml
index a1001559..2d06a4e5 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "AssociativeWindowAggregation"
 uuid = "444271a7-5434-4a02-b82b-0e30a9223c60"
 authors = ["Tom Gillam <tpgillam@googlemail.com>"]
-version = "0.4.0"
+version = "0.4.1"
 
 [deps]
 DataStructures = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
diff --git a/src/time.jl b/src/time.jl
index ba48b7a4..d4bc5c2f 100644
--- a/src/time.jl
+++ b/src/time.jl
@@ -46,7 +46,7 @@ mutable struct TimeWindowAssociativeOp{Value,Op,Op!,Time,TimeDiff}
     end
 end
 
-function TimeWindowAssociativeOp{T,Op,Time}(window::TimeDiff) where {T,Op,Time,TimeDiff}
+function TimeWindowAssociativeOp{T,Op,Time}(window) where {T,Op,Time}
     return TimeWindowAssociativeOp{T,Op,Op,Time}(window)
 end