Index: kernel/generic/src/ipc/ipc.c
===================================================================
--- kernel/generic/src/ipc/ipc.c	(revision 8a637a47d260c9852eb7bbefc705cba01e8ef051)
+++ kernel/generic/src/ipc/ipc.c	(revision 6d351e674a67b6ecee3c205c0f09e29e92b462be)
@@ -77,4 +77,5 @@
 	call->forget = false;
 	call->sender = NULL;
+	call->callerbox = &TASK->answerbox;
 	call->buffer = NULL;
 }
@@ -220,5 +221,5 @@
 	spinlock_unlock(&call->forget_lock);
 
-	answerbox_t *callerbox = &call->sender->answerbox;
+	answerbox_t *callerbox = call->callerbox;
 	bool do_lock = ((!selflocked) || (callerbox != &TASK->answerbox));