diff --git a/plume-common/Cargo.toml b/plume-common/Cargo.toml
index befe7d3c..88889988 100644
--- a/plume-common/Cargo.toml
+++ b/plume-common/Cargo.toml
@@ -25,6 +25,7 @@ regex-syntax = { version = "0.6.17", default-features = false, features = ["unic
 tracing = "0.1.34"
 askama_escape = "0.10.3"
 activitystreams = "0.7.0-alpha.18"
+activitystreams-ext = "0.1.0-alpha.2"
 
 [dependencies.chrono]
 features = ["serde"]