diff --git a/rfctime/rfc3339.go b/rfctime/rfc3339.go
index e493f55..0e350ff 100644
--- a/rfctime/rfc3339.go
+++ b/rfctime/rfc3339.go
@@ -66,6 +66,10 @@ func (t *RFC3339Time) UnmarshalText(data []byte) error {
 }
 
 func (t *RFC3339Time) UnmarshalBSONValue(bt bsontype.Type, data []byte) error {
+	if bt == bsontype.Null {
+		*t = RFC3339Time{}
+		return nil
+	}
 	if bt != bsontype.DateTime {
 		return errors.New(fmt.Sprintf("cannot unmarshal %v into RFC3339Time", bt))
 	}
diff --git a/rfctime/rfc3339Nano.go b/rfctime/rfc3339Nano.go
index a14b856..8383b32 100644
--- a/rfctime/rfc3339Nano.go
+++ b/rfctime/rfc3339Nano.go
@@ -66,6 +66,10 @@ func (t *RFC3339NanoTime) UnmarshalText(data []byte) error {
 }
 
 func (t *RFC3339NanoTime) UnmarshalBSONValue(bt bsontype.Type, data []byte) error {
+	if bt == bsontype.Null {
+		*t = RFC3339NanoTime{}
+		return nil
+	}
 	if bt != bsontype.DateTime {
 		return errors.New(fmt.Sprintf("cannot unmarshal %v into RFC3339NanoTime", bt))
 	}