diff --git a/token.go b/token.go
index 24d4c6e..42e7e00 100644
--- a/token.go
+++ b/token.go
@@ -236,7 +236,8 @@ func (t *tokenizer) back() {
 
 	if t.source[t.index] == '\n' {
 		t.line--
-		// TODO: reset col correctly
+		lines := strings.Split(string(t.source), "\n")
+		t.col = len(lines[t.line])
 	} else {
 		t.col--
 	}
diff --git a/token_test.go b/token_test.go
new file mode 100644
index 0000000..5daf0ce
--- /dev/null
+++ b/token_test.go
@@ -0,0 +1,16 @@
+package main
+
+import "testing"
+
+func TestBack(t *testing.T) {
+	token := tokenizer{
+		source: []rune("hello\nworld"),
+		line:   1,
+		col:    0,
+		index:  6,
+	}
+	token.back()
+	if token.line != 0 && token.col != 5 {
+		t.Errorf("Expected line 0 and column 5, received line %d and column %d", token.line, token.col)
+	}
+}