diff --git a/release-plz.toml b/release-plz.toml
index d93045609..600685028 100644
--- a/release-plz.toml
+++ b/release-plz.toml
@@ -61,4 +61,6 @@ version_group = "hugr"
 [[package]]
 name = "hugr-model"
 release = true
-version_group = "hugr"
+# Use a separate version group while the dependency is `-unstable`,
+# to avoid breaking releases of the main package.
+version_group = "hugr-model"