Index: kernel/generic/include/ipc/ipc.h
===================================================================
--- kernel/generic/include/ipc/ipc.h	(revision fc0de8c33fadd1f6730eb0465b89c7afa861fe56)
+++ kernel/generic/include/ipc/ipc.h	(revision a2700269a26215d1d65e027459823e351f3f4553)
@@ -71,5 +71,5 @@
 	struct call *hangup_call;
 	ipc_phone_state_t state;
-	atomic_t active_calls;
+	atomic_size_t active_calls;
 	/** User-defined label */
 	sysarg_t label;
@@ -90,5 +90,5 @@
 	 * Number of answers the answerbox is expecting to eventually arrive.
 	 */
-	atomic_t active_calls;
+	atomic_size_t active_calls;
 
 	/** Phones connected to this answerbox. */