diff --git a/include/l4/generic/space.h b/include/l4/generic/space.h
index 8e4f3a5..1c6adeb 100644
--- a/include/l4/generic/space.h
+++ b/include/l4/generic/space.h
@@ -41,12 +41,7 @@ struct address_space {
 
 struct address_space_list {
 	struct link list;
-
-	/* Lock for list add/removal */
-	struct spinlock list_lock;
-
-	/* Used when delete/creating spaces */
-	struct mutex ref_lock;
+	struct mutex lock;
 	int count;
 };
 
@@ -56,8 +51,6 @@ void address_space_attach(struct ktcb *tcb, struct address_space *space);
 struct address_space *address_space_find(l4id_t spid);
 void address_space_add(struct address_space *space);
 void address_space_remove(struct address_space *space);
-void address_space_reference_lock();
-void address_space_reference_unlock();
 void init_address_space_list(struct address_space_list *space_list);
 int check_access(unsigned long vaddr, unsigned long size,
 		 unsigned int flags, int page_in);
diff --git a/src/api/thread.c b/src/api/thread.c
index c0b8dd4..11bf8a4 100644
--- a/src/api/thread.c
+++ b/src/api/thread.c
@@ -271,30 +271,38 @@ int thread_setup_space(struct ktcb *tcb, struct task_ids *ids, unsigned int flag
 	struct address_space *space, *new;
 	int ret = 0;
 
-	address_space_reference_lock();
-
 	if (flags & TC_SHARE_SPACE) {
+		mutex_lock(&curcont->space_list.lock);
 		if (!(space = address_space_find(ids->spid))) {
+			mutex_unlock(&curcont->space_list.lock);
 			ret = -ESRCH;
 			goto out;
 		}
+		mutex_lock(&space->lock);
+		mutex_unlock(&curcont->space_list.lock);
 		address_space_attach(tcb, space);
+		mutex_unlock(&space->lock);
 	}
-	if (flags & TC_COPY_SPACE) {
+	else if (flags & TC_COPY_SPACE) {
+		mutex_lock(&curcont->space_list.lock);
 		if (!(space = address_space_find(ids->spid))) {
 			ret = -ESRCH;
 			goto out;
 		}
+		mutex_lock(&space->lock);
 		if (IS_ERR(new = address_space_create(space))) {
+			mutex_unlock(&curcont->space_list.lock);
+			mutex_unlock(&space->lock);
 			ret = (int)new;
 			goto out;
 		}
-		/* New space id to be returned back to caller */
-		ids->spid = new->spid;
+		mutex_unlock(&space->lock);
+		ids->spid = new->spid; 	/* Return newid to caller */
 		address_space_attach(tcb, new);
 		address_space_add(new);
+		mutex_unlock(&curcont->space_list.lock);
 	}
-	if (flags & TC_NEW_SPACE) {
+	else if (flags & TC_NEW_SPACE) {
 		if (IS_ERR(new = address_space_create(0))) {
 			ret = (int)new;
 			goto out;
@@ -302,11 +310,12 @@ int thread_setup_space(struct ktcb *tcb, struct task_ids *ids, unsigned int flag
 		/* New space id to be returned back to caller */
 		ids->spid = new->spid;
 		address_space_attach(tcb, new);
+		mutex_lock(&curcont->space_list.lock);
 		address_space_add(new);
+		mutex_unlock(&curcont->space_list.lock);
 	}
 
 out:
-	address_space_reference_unlock();
 	return ret;
 }
 
diff --git a/src/generic/space.c b/src/generic/space.c
index db5d033..200f89f 100644
--- a/src/generic/space.c
+++ b/src/generic/space.c
@@ -20,19 +20,8 @@ void init_address_space_list(struct address_space_list *space_list)
 {
 	memset(space_list, 0, sizeof(*space_list));
 
-	mutex_init(&space_list->ref_lock);
-	spin_lock_init(&space_list->list_lock);
 	link_init(&space_list->list);
-}
-
-void address_space_reference_lock()
-{
-	mutex_lock(&curcont->space_list.ref_lock);
-}
-
-void address_space_reference_unlock()
-{
-	mutex_unlock(&curcont->space_list.ref_lock);
+	mutex_init(&space_list->lock);
 }
 
 void address_space_attach(struct ktcb *tcb, struct address_space *space)
@@ -45,38 +34,24 @@ struct address_space *address_space_find(l4id_t spid)
 {
 	struct address_space *space;
 
-	spin_lock(&curcont->space_list.list_lock);
-	list_foreach_struct(space, &curcont->space_list.list, list) {
-		if (space->spid == spid) {
-			spin_unlock(&curcont->space_list.list_lock);
+	list_foreach_struct(space, &curcont->space_list.list, list)
+		if (space->spid == spid)
 			return space;
-		}
-	}
-	spin_unlock(&curcont->space_list.list_lock);
 	return 0;
 }
 
 void address_space_add(struct address_space *space)
 {
-	spin_lock(&curcont->space_list.list_lock);
 	BUG_ON(!list_empty(&space->list));
 	list_insert(&space->list, &curcont->space_list.list);
 	BUG_ON(!++curcont->space_list.count);
-	spin_unlock(&curcont->space_list.list_lock);
 }
 
 void address_space_remove(struct address_space *space)
 {
-	spin_lock(&curcont->space_list.list_lock);
-
-	/*
-	 * If current is quitting as the last task of this space,
-	 * its tcb may already be removed, and this is fine
-	 */
-	BUG_ON(list_empty(&space->list) && space != current->space);
+	BUG_ON(list_empty(&space->list));
 	BUG_ON(--curcont->space_list.count < 0);
 	list_remove_init(&space->list);
-	spin_unlock(&curcont->space_list.list_lock);
 }
 
 /* Assumes address space reflock is already held */
diff --git a/src/generic/tcb.c b/src/generic/tcb.c
index 42c49d4..47dcab4 100644
--- a/src/generic/tcb.c
+++ b/src/generic/tcb.c
@@ -77,21 +77,21 @@ void tcb_delete(struct ktcb *tcb)
 	BUG_ON(tcb->waiting_on);
 	BUG_ON(tcb->wq);
 
-	/*
-	 * Take this lock as we may delete
-	 * the address space as well
-	 */
-	address_space_reference_lock();
+	mutex_lock(&curcont->space_list.lock);
+	mutex_lock(&tcb->space->lock);
 	BUG_ON(--tcb->space->ktcb_refs < 0);
 
 	/* No refs left for the space, delete it */
 	if (tcb->space->ktcb_refs == 0) {
 		address_space_remove(tcb->space);
+		mutex_unlock(&tcb->space->lock);
 		address_space_delete(tcb->space);
+		mutex_unlock(&curcont->space_list.lock);
+	} else {
+		mutex_unlock(&tcb->space->lock);
+		mutex_unlock(&curcont->space_list.lock);
 	}
 
-	address_space_reference_unlock();
-
 	/* Deallocate tcb ids */
 	id_del(&kernel_resources.ktcb_ids, tcb->tid);