diff --git a/person.go b/person.go
index 4e51be6..bf947bd 100644
--- a/person.go
+++ b/person.go
@@ -18,9 +18,11 @@ func (p *Person) Check() error {
 		return errors.New("name element of person element empty")
 	}
 
-	for i, e := range p.Extensions {
-		if err := e.Check(); err != nil {
-			return fmt.Errorf("extension element %v of person %v: %v", i, p.Name, err)
+	if p.Extensions != nil {
+		for i, e := range p.Extensions {
+			if err := e.Check(); err != nil {
+				return fmt.Errorf("extension element %v of person %v: %v", i, p.Name, err)
+			}
 		}
 	}