Index: uspace/lib/libc/generic/ipc.c
===================================================================
--- uspace/lib/libc/generic/ipc.c	(revision a55d5f9fbe9f149843781206c69705643f929991)
+++ uspace/lib/libc/generic/ipc.c	(revision ff9244a50908fdf6a76f151cae83e6d253d15921)
@@ -690,5 +690,6 @@
  * @param callid	Storage where the hash of the IPC_M_DATA_READ call will
  * 			be stored.
- * @param size		Storage where the maximum size will be stored.
+ * @param size		Storage where the maximum size will be stored. Can be
+ *			NULL.
  *
  * @return		Non-zero on success, zero on failure.
@@ -703,6 +704,6 @@
 	if (IPC_GET_METHOD(data) != IPC_M_DATA_READ)
 		return 0;
-	assert(size);
-	*size = (size_t) IPC_GET_ARG2(data);
+	if (size)
+		*size = (size_t) IPC_GET_ARG2(data);
 	return 1;
 }