diff --git a/net/webrtc/src/webrtcsrc/imp.rs b/net/webrtc/src/webrtcsrc/imp.rs
index 6923a99a..b779facf 100644
--- a/net/webrtc/src/webrtcsrc/imp.rs
+++ b/net/webrtc/src/webrtcsrc/imp.rs
@@ -240,7 +240,7 @@ impl ObjectImpl for BaseWebRTCSrc {
                  */
                 glib::subclass::Signal::builder("request-encoded-filter")
                     .param_types([
-                        String::static_type(),
+                        Option::<String>::static_type(),
                         String::static_type(),
                         Option::<gst::Caps>::static_type(),
                     ])