diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9e4a5a5..c9b4b72 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,6 @@
 # Changelog
 
-- v0.4.0
+- v0.3.1
     - use a more efficient data structure to store cigar operations.
     - slight speed improvement.
 - v0.3.0
diff --git a/wfa-go/wfa-go.go b/wfa-go/wfa-go.go
index 25a0e84..4fa6cf6 100644
--- a/wfa-go/wfa-go.go
+++ b/wfa-go/wfa-go.go
@@ -31,7 +31,7 @@ import (
 	"github.com/shenwei356/wfa"
 )
 
-var version = "0.4.0"
+var version = "0.3.1"
 
 func main() {
 	app := filepath.Base(os.Args[0])