diff --git a/tasks/fs0/src/syscalls.c b/tasks/fs0/src/syscalls.c
index 5037f92..eaeae41 100644
--- a/tasks/fs0/src/syscalls.c
+++ b/tasks/fs0/src/syscalls.c
@@ -26,9 +26,9 @@ int send_pager_opendata(l4id_t sender, int fd, unsigned long vnum)
 {
 	int err;
 
-	write_mr(sender, L4SYS_ARG0);
-	write_mr(fd, L4SYS_ARG1);
-	write_mr(vnum, L4SYS_ARG2);
+	write_mr(L4SYS_ARG0, sender);
+	write_mr(L4SYS_ARG1, fd);
+	write_mr(L4SYS_ARG2, vnum);
 
 	if ((err = l4_send(PAGER_TID, L4_IPC_TAG_OPENDATA)) < 0) {
 		printf("%s: L4 IPC Error: %d.\n", __FUNCTION__, err);
diff --git a/tasks/libl4/include/l4lib/arch-arm/message.h b/tasks/libl4/include/l4lib/arch-arm/message.h
index 0e03a6c..ed893a5 100644
--- a/tasks/libl4/include/l4lib/arch-arm/message.h
+++ b/tasks/libl4/include/l4lib/arch-arm/message.h
@@ -10,7 +10,7 @@ static inline unsigned int read_mr(int offset)
 	return __L4_ARM_Utcb()->mr[offset];
 }
 
-static inline void write_mr(unsigned int val, unsigned int offset)
+static inline void write_mr(unsigned int offset, unsigned int val)
 {
 	__L4_ARM_Utcb()->mr[offset] = val;
 }
diff --git a/tasks/libl4/include/l4lib/arch-arm/syslib.h b/tasks/libl4/include/l4lib/arch-arm/syslib.h
index aa68300..4de46f5 100644
--- a/tasks/libl4/include/l4lib/arch-arm/syslib.h
+++ b/tasks/libl4/include/l4lib/arch-arm/syslib.h
@@ -39,7 +39,7 @@ static inline l4id_t l4_get_sender(void)
 
 static inline void l4_set_sender(l4id_t id)
 {
-	write_mr((unsigned int)id, MR_SENDER);
+	write_mr(MR_SENDER, (unsigned int)id);
 }
 
 static inline unsigned int l4_get_tag(void)
@@ -49,7 +49,7 @@ static inline unsigned int l4_get_tag(void)
 
 static inline void l4_set_tag(unsigned int tag)
 {
-	write_mr(tag, MR_TAG);
+	write_mr(MR_TAG, tag);
 }
 
 static inline l4id_t self_tid(void)
diff --git a/tasks/mm0/src/task.c b/tasks/mm0/src/task.c
index d8b42d2..356f7ed 100644
--- a/tasks/mm0/src/task.c
+++ b/tasks/mm0/src/task.c
@@ -207,13 +207,13 @@ void send_task_data(l4id_t requester)
 	}
 
 	/* First word is total number of tcbs */
-	write_mr(tcb_head.total, L4SYS_ARG0);
+	write_mr(L4SYS_ARG0, tcb_head.total);
 
 	/* Write each tcb's tid */
 	li = 0;
 	list_for_each_entry(t, &tcb_head.list, list) {
 		BUG_ON(li >= MR_USABLE_TOTAL);
-		write_mr(t->tid, L4SYS_ARG1 + li);
+		write_mr(L4SYS_ARG1 + li, t->tid);
 		li++;
 	}