diff --git a/errors.go b/errors.go
index 978b555b..53ea9439 100644
--- a/errors.go
+++ b/errors.go
@@ -56,8 +56,6 @@ const (
 )
 
 var (
-	errDriver = errors.New("internal driver error: please file a bug report")
-
 	errAPI        = errors.New("API error")
 	errVectorSize = errors.New("data chunks cannot exceed duckdb's internal vector size")
 
diff --git a/errors_test.go b/errors_test.go
index dac9d6dd..2e23933b 100644
--- a/errors_test.go
+++ b/errors_test.go
@@ -56,6 +56,8 @@ func TestErrNestedMap(t *testing.T) {
 }
 
 func TestErrAppender(t *testing.T) {
+	t.Parallel()
+
 	t.Run(errAppenderInvalidCon.Error(), func(t *testing.T) {
 		var con driver.Conn
 		_, err := NewAppenderFromConn(con, "", "test")
@@ -160,6 +162,13 @@ func TestErrAppender(t *testing.T) {
 		require.NoError(t, con.Close())
 		require.NoError(t, c.Close())
 	})
+
+	t.Run(errUnsupportedMapKeyType.Error(), func(t *testing.T) {
+		c, con, a := prepareAppender(t, `CREATE TABLE test (m MAP(INT[], STRUCT(v INT)))`)
+		err := a.AppendRow(nil)
+		testError(t, err, errAppenderAppendRow.Error(), errUnsupportedMapKeyType.Error())
+		cleanupAppender(t, c, con, a)
+	})
 }
 
 func TestErrAppend(t *testing.T) {
@@ -186,10 +195,8 @@ func TestErrAppendDecimal(t *testing.T) {
 
 func TestErrAppendEnum(t *testing.T) {
 	c, con, a := prepareAppender(t, testTypesEnumSQL+";"+`CREATE TABLE test (e my_enum)`)
-
 	err := a.AppendRow("3")
 	testError(t, err, errAppenderAppendRow.Error(), castErrMsg)
-
 	cleanupAppender(t, c, con, a)
 }
 
diff --git a/vector.go b/vector.go
index 7094c118..e7e1d57c 100644
--- a/vector.go
+++ b/vector.go
@@ -404,7 +404,6 @@ func (vec *vector) initCString(duckdbType C.duckdb_type) {
 }
 
 func (vec *vector) initDecimal(logicalType C.duckdb_logical_type, colIdx int) error {
-	// Get the width and scale.
 	vec.width = uint8(C.duckdb_decimal_width(logicalType))
 	vec.scale = uint8(C.duckdb_decimal_scale(logicalType))