diff --git a/python/Cargo.toml b/python/Cargo.toml
index c23db88..a4977a0 100644
--- a/python/Cargo.toml
+++ b/python/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "pytextspan"
-version = "0.5.0"
+version = "0.5.1"
 authors = ["Yohei Tamura <tamuhey@gmail.com>"]
 edition = "2018"
 
diff --git a/python/pyproject.toml b/python/pyproject.toml
index e831d93..9ed16a1 100644
--- a/python/pyproject.toml
+++ b/python/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "poetry.masonry.api"
 
 [tool.poetry]
 name = "pytextspan"
-version = "0.5.0"
+version = "0.5.1"
 description = ""
 authors = [ "Yohei Tamura <tamuhey@gmail.com>",]
 license = "MIT"
diff --git a/python/src/lib.rs b/python/src/lib.rs
index a3c2668..d60eb64 100644
--- a/python/src/lib.rs
+++ b/python/src/lib.rs
@@ -3,7 +3,7 @@ use textspan::Span;
 
 #[pymodule]
 fn textspan(_py: Python, m: &PyModule) -> PyResult<()> {
-    m.add("__version__", "0.5.0")?;
+    m.add("__version__", "0.5.1")?;
 
     /// Converts the spans defined in `text` to those defined in `original_text`.
     ///