diff --git a/libpkgconf/cache.c b/libpkgconf/cache.c
index 1662ce5..fa8b3b3 100644
--- a/libpkgconf/cache.c
+++ b/libpkgconf/cache.c
@@ -44,7 +44,7 @@
  *    :rtype: pkgconf_pkg_t *
  */
 pkgconf_pkg_t *
-pkgconf_cache_lookup(const pkgconf_client_t *client, const char *id)
+pkgconf_cache_lookup(pkgconf_client_t *client, const char *id)
 {
 	pkgconf_node_t *node;
 
diff --git a/libpkgconf/libpkgconf.h b/libpkgconf/libpkgconf.h
index ac873bf..30f52a7 100644
--- a/libpkgconf/libpkgconf.h
+++ b/libpkgconf/libpkgconf.h
@@ -136,6 +136,8 @@ struct pkgconf_pkg_ {
 	pkgconf_list_t vars;
 
 	unsigned int flags;
+
+	pkgconf_client_t *owner;
 };
 
 typedef bool (*pkgconf_pkg_iteration_func_t)(const pkgconf_pkg_t *pkg, void *data);
@@ -242,7 +244,7 @@ PKGCONF_API bool pkgconf_default_error_handler(const char *msg, const pkgconf_cl
 	} while (0);
 #endif
 
-PKGCONF_API pkgconf_pkg_t *pkgconf_pkg_ref(const pkgconf_client_t *client, pkgconf_pkg_t *pkg);
+PKGCONF_API pkgconf_pkg_t *pkgconf_pkg_ref(pkgconf_client_t *client, pkgconf_pkg_t *pkg);
 PKGCONF_API void pkgconf_pkg_unref(pkgconf_client_t *client, pkgconf_pkg_t *pkg);
 PKGCONF_API void pkgconf_pkg_free(pkgconf_client_t *client, pkgconf_pkg_t *pkg);
 PKGCONF_API pkgconf_pkg_t *pkgconf_pkg_find(pkgconf_client_t *client, const char *name);
@@ -306,7 +308,7 @@ PKGCONF_API bool pkgconf_queue_apply(pkgconf_client_t *client, pkgconf_list_t *l
 PKGCONF_API bool pkgconf_queue_validate(pkgconf_client_t *client, pkgconf_list_t *list, int maxdepth);
 
 /* cache.c */
-PKGCONF_API pkgconf_pkg_t *pkgconf_cache_lookup(const pkgconf_client_t *client, const char *id);
+PKGCONF_API pkgconf_pkg_t *pkgconf_cache_lookup(pkgconf_client_t *client, const char *id);
 PKGCONF_API void pkgconf_cache_add(pkgconf_client_t *client, pkgconf_pkg_t *pkg);
 PKGCONF_API void pkgconf_cache_remove(pkgconf_client_t *client, pkgconf_pkg_t *pkg);
 PKGCONF_API void pkgconf_cache_free(pkgconf_client_t *client);
diff --git a/libpkgconf/pkg.c b/libpkgconf/pkg.c
index cc1edda..f883623 100644
--- a/libpkgconf/pkg.c
+++ b/libpkgconf/pkg.c
@@ -475,10 +475,12 @@ pkgconf_pkg_free(pkgconf_client_t *client, pkgconf_pkg_t *pkg)
  *    :rtype: pkgconf_pkg_t *
  */
 pkgconf_pkg_t *
-pkgconf_pkg_ref(const pkgconf_client_t *client, pkgconf_pkg_t *pkg)
+pkgconf_pkg_ref(pkgconf_client_t *client, pkgconf_pkg_t *pkg)
 {
-	(void) client;
+	if (pkg->owner != NULL && pkg->owner != client)
+		PKGCONF_TRACE(client, "WTF: client %p refers to package %p owned by other client %p", client, pkg, pkg->owner);
 
+	pkg->owner = client;
 	pkg->refcount++;
 	PKGCONF_TRACE(client, "refcount@%p: %d", pkg, pkg->refcount);
 
@@ -499,11 +501,14 @@ pkgconf_pkg_ref(const pkgconf_client_t *client, pkgconf_pkg_t *pkg)
 void
 pkgconf_pkg_unref(pkgconf_client_t *client, pkgconf_pkg_t *pkg)
 {
+	if (pkg->owner != NULL && pkg->owner != client)
+		PKGCONF_TRACE(client, "WTF: client %p unrefs package %p owned by other client %p", client, pkg, pkg->owner);
+
 	pkg->refcount--;
-	PKGCONF_TRACE(client, "refcount@%p: %d", pkg, pkg->refcount);
+	PKGCONF_TRACE(pkg->owner, "refcount@%p: %d", pkg, pkg->refcount);
 
 	if (pkg->refcount <= 0)
-		pkgconf_pkg_free(client, pkg);
+		pkgconf_pkg_free(pkg->owner, pkg);
 }
 
 static inline pkgconf_pkg_t *