Index: src/libcfa/concurrency/kernel.c
===================================================================
--- src/libcfa/concurrency/kernel.c	(revision 3bb51e112144273d0beaa9cc3665fd5e23a42e4a)
+++ src/libcfa/concurrency/kernel.c	(revision ead8c7e2a0589916d2a0faeb5525f3255cf94858)
@@ -456,13 +456,10 @@
 
 void append( simple_thread_list * this, thread * t ) {
-	assert( t->next == NULL );
 	assert(this->tail != NULL);
 	*this->tail = t;
 	this->tail = &t->next;
-	assert(this->tail != NULL);
 }
 
 thread * pop_head( simple_thread_list * this ) {
-	assert(this->tail != NULL);
 	thread * head = this->head;
 	if( head ) {
@@ -473,5 +470,4 @@
 		head->next = NULL;
 	}	
-	assert(this->tail != NULL);
 	return head;
 }
Index: src/libcfa/concurrency/monitor.c
===================================================================
--- src/libcfa/concurrency/monitor.c	(revision 3bb51e112144273d0beaa9cc3665fd5e23a42e4a)
+++ src/libcfa/concurrency/monitor.c	(revision ead8c7e2a0589916d2a0faeb5525f3255cf94858)
@@ -23,6 +23,4 @@
 	thread * thrd = this_thread();
 
-	assert( this->entry_queue.tail != NULL );
-
 	if( this->holder ) {
 		append( &this->entry_queue, thrd );
@@ -34,6 +32,4 @@
 	}
 
-	assert( this->entry_queue.tail != NULL );	
-
 	unlock( &this->lock );
 }
@@ -42,6 +38,4 @@
 	lock( &this->lock );
 
-	assert( this->entry_queue.tail != NULL );	
-
 	thread * thrd = this_thread();
 	assert( thrd == this->holder );
@@ -49,6 +43,4 @@
 	this->holder = pop_head( &this->entry_queue );
 
-	assert( this->entry_queue.tail != NULL );	
-
 	unlock( &this->lock );
 	if( this->holder ) ScheduleThread( this->holder );