diff --git a/Concurrent Systems/test/Untitled.md b/Concurrent Systems/test/Untitled.md
index d28100e..b0aef03 100644
--- a/Concurrent Systems/test/Untitled.md	
+++ b/Concurrent Systems/test/Untitled.md	
@@ -3,10 +3,12 @@ GLOB_MUTEX and R_MUTEX semaphores init. at 1
 R a shared register init. at 0
 
 begin_read() :=
+	PRIO_MUTEX.down()
 	R_MUTEX.down()
 	R++ # currently active readers
 	if R = 1 then GLOB_MUTEX.down()
 	R_MUTEX.up()
+	PRIO_MUTEX.up()
 	return
 
 end_read() :=