diff --git a/marshal.go b/marshal.go
index 0b9c08f..f31bf2c 100644
--- a/marshal.go
+++ b/marshal.go
@@ -186,6 +186,20 @@ func (p *Encoder) marshal(val reflect.Value) cfValue {
 			}
 		}
 		return dict
+	case reflect.Interface, reflect.Ptr:
+		// Attempt to marshal the underlying type of the interface
+		if val.CanInterface() {
+			if inter := val.Interface(); inter != nil {
+				// Pointer to interface
+				interptr := reflect.New(reflect.TypeOf(inter))
+				// Elem requires an Interface or Pointer
+				if elem := interptr.Elem(); elem.IsValid() && elem.CanSet() {
+					elem.Set(reflect.ValueOf(inter))
+					return p.marshal(reflect.Indirect(interptr))
+				}
+			}
+		}
+		panic(&unknownTypeError{typ})
 	default:
 		panic(&unknownTypeError{typ})
 	}
diff --git a/marshal_test.go b/marshal_test.go
index 4509909..cd83777 100644
--- a/marshal_test.go
+++ b/marshal_test.go
@@ -103,3 +103,33 @@ func TestInterfaceFieldMarshal(t *testing.T) {
 		t.Log("expect non-zero data")
 	}
 }
+
+type Dog struct {
+	Name string
+}
+
+type Animal interface{}
+
+func TestInterfaceSliceMarshal(t *testing.T) {
+	x := make([]Animal, 0)
+	x = append(x, &Dog{Name: "dog"})
+
+	b, err := Marshal(x, XMLFormat)
+	if err != nil {
+		t.Error(err)
+	} else if len(b) == 0 {
+		t.Error("expect non-zero data")
+	}
+}
+
+func TestInterfaceGeneralSliceMarshal(t *testing.T) {
+	x := make([]interface{}, 0) // accept any type
+	x = append(x, &Dog{Name: "dog"}, "a string", 1, true)
+
+	b, err := Marshal(x, XMLFormat)
+	if err != nil {
+		t.Error(err)
+	} else if len(b) == 0 {
+		t.Error("expect non-zero data")
+	}
+}