diff --git a/dot/dot.go b/dot/dot.go
index 03ca4e1..14dd7f7 100644
--- a/dot/dot.go
+++ b/dot/dot.go
@@ -71,7 +71,13 @@ func writeAttrs(w *bytes.Buffer, name string, tabs int, attrs map[string]interfa
 	sort.Sort(keys)
 	list := []string{}
 	for _, k := range keys {
-		list = append(list, fmt.Sprintf("%s=%v", k, attrs[k]))
+		v := attrs[k]
+		switch value := v.(type) {
+		case string:
+			list = append(list, fmt.Sprintf("%s=%q", k, value))
+		default:
+			list = append(list, fmt.Sprintf("%s=%v", k, value))
+		}
 	}
 	fmt.Fprintln(w, strings.Join(list, ", "), "];")
 }
diff --git a/dot/dot_test.go b/dot/dot_test.go
index d5c139e..f2f018f 100644
--- a/dot/dot_test.go
+++ b/dot/dot_test.go
@@ -39,14 +39,14 @@ func TestDirectedDotWriter(t *testing.T) {
 
 	expected := `digraph {
 	graph [ splines=false ];
-	0 [ label=Happy ];
-	1 [ label=Sleepy, shape=egg ];
+	0 [ label="Happy" ];
+	1 [ label="Sleepy", shape="egg" ];
 	1 -> 0;
 	1 -> 2;
 	3 -> 1;
 	4 -> 3;
 	4 -> 5;
-	5 -> 6 [ arrowhead=diamond ];
+	5 -> 6 [ arrowhead="diamond" ];
 	6 -> 7;
 	6 -> 9;
 	9 -> 8;