diff --git a/src/calls-manager.c b/src/calls-manager.c
index b0c1af1..b3764a6 100644
--- a/src/calls-manager.c
+++ b/src/calls-manager.c
@@ -146,7 +146,9 @@ ussd_state_changed_cb (CallsManager *self,
 static void
 add_origin (CallsManager *self, CallsOrigin *origin, CallsProvider *provider)
 {
-  g_return_if_fail (CALLS_IS_ORIGIN (origin));
+  g_assert (CALLS_IS_MANAGER (self));
+  g_assert (CALLS_IS_ORIGIN (origin));
+  g_assert (CALLS_IS_PROVIDER (provider));
 
   g_signal_connect_swapped (origin, "call-added", G_CALLBACK (add_call), self);
   g_signal_connect_swapped (origin, "call-removed", G_CALLBACK (remove_call), self);