diff --git a/go.mod b/go.mod
index 8d01bea..14aee94 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module go.tmz.dev/musttag
 
-go 1.21
+go 1.20
 
 require (
 	go-simpler.org/assert v0.7.0
diff --git a/go.sum b/go.sum
index 82bf77c..3e49224 100644
--- a/go.sum
+++ b/go.sum
@@ -3,7 +3,6 @@ go-simpler.org/assert v0.7.0/go.mod h1:74Eqh5eI6vCK6Y5l3PI8ZYFXG4Sa+tkr70OIPJAUr
 golang.org/x/mod v0.13.0 h1:I/DsJXRlw/8l/0c24sM9yb0T4z9liZTduXvdAWYiysY=
 golang.org/x/mod v0.13.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.4.0 h1:zxkM55ReGkDlKSM+Fu41A+zmbZuaPVbGMzvvdUPznYQ=
-golang.org/x/sync v0.4.0/go.mod h1:FU7BRWz2tNW+3quACPkgCx/L+uEAv1htQ0V83Z9Rj+Y=
 golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
 golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/tools v0.14.0 h1:jvNa2pY0M4r62jkRQ6RwEZZyPcymeL9XZMLBbV7U2nc=
diff --git a/testdata/src/custom/go.mod b/testdata/src/custom/go.mod
index 6514bde..d02792e 100644
--- a/testdata/src/custom/go.mod
+++ b/testdata/src/custom/go.mod
@@ -1,3 +1,3 @@
 module example.com/custom
 
-go 1.21
+go 1.20
diff --git a/testdata/src/go.mod b/testdata/src/go.mod
index 62766c8..6eb80d2 100644
--- a/testdata/src/go.mod
+++ b/testdata/src/go.mod
@@ -1,6 +1,6 @@
 module tests
 
-go 1.21
+go 1.20
 
 require (
 	example.com/custom v0.1.0
diff --git a/testdata/src/go.work b/testdata/src/go.work
index 04b5a79..614654c 100644
--- a/testdata/src/go.work
+++ b/testdata/src/go.work
@@ -1,4 +1,4 @@
-go 1.21
+go 1.20
 
 use (
 	.