diff --git a/Readme.md b/Readme.md
index f4051e9..0f4f585 100644
--- a/Readme.md
+++ b/Readme.md
@@ -12,7 +12,7 @@ Use the [Nimble][3] package manager to add `questionable` to an existing
 project. Add the following to its .nimble file:
 
 ```nim
-requires "questionable >= 0.3.0 & < 0.4.0"
+requires "questionable >= 0.4.0 & < 0.5.0"
 ```
 
 If you want to make use of Result types, then you also have to add either the
diff --git a/questionable.nimble b/questionable.nimble
index c38dab5..1d4891a 100644
--- a/questionable.nimble
+++ b/questionable.nimble
@@ -1,4 +1,4 @@
-version = "0.3.0"
+version = "0.4.0"
 author = "Questionable Authors"
 description = "Elegant optional types"
 license = "MIT"