diff --git a/Interlace/lib/core/input.py b/Interlace/lib/core/input.py
index 21b36dd..439dd33 100644
--- a/Interlace/lib/core/input.py
+++ b/Interlace/lib/core/input.py
@@ -112,9 +112,11 @@ class InputHelper(object):
                 if task_name == new_task_name:
                     return task_block
                 # otherwise pre-process all the commands in this new `new_task_name` block
-                for task in InputHelper._pre_process_commands(command_list, new_task_name, False):
+                tasks = InputHelper._pre_process_commands(command_list, new_task_name, False)
+                for task in tasks:
                     task_block.append(task)
-                    sibling = task
+                if len(tasks) > 0:
+                    sibling = tasks[-1]
                 continue
             else:
                 # if a blocker is encountered, all commands following the blocker must wait until the last
@@ -126,10 +128,10 @@ class InputHelper(object):
                 # if we're in the global scope and there was a previous _blocker_ encountered, we wait for the last
                 # child of the block
                 if is_global_task and global_task:
-                    task.wait_for(global_task.get_lock())
+                    task.wait_for(task_block)
                 # all but the first command in a block scope wait for its predecessor
                 elif sibling and not is_global_task:
-                    task.wait_for(sibling.get_lock())
+                    task.wait_for([sibling])
                 task_block.append(task)
                 sibling = task
         return task_block
diff --git a/Interlace/lib/threader.py b/Interlace/lib/threader.py
index 26d11df..8129a48 100644
--- a/Interlace/lib/threader.py
+++ b/Interlace/lib/threader.py
@@ -9,7 +9,7 @@ class Task(object):
     def __init__(self, command):
         self.task = command
         self.self_lock = None
-        self.sibling_lock = None
+        self.sibling_locks = []
 
     def __cmp__(self, other):
         return self.name() == other.name()
@@ -20,21 +20,22 @@ class Task(object):
     def clone(self):
         new_task = Task(self.task)
         new_task.self_lock = self.self_lock
-        new_task.sibling_lock = self.sibling_lock
+        new_task.sibling_locks = self.sibling_locks
         return new_task
 
     def replace(self, old, new):
         self.task = self.task.replace(old, new)
 
     def run(self, t=False):
-        if self.sibling_lock:
-            self.sibling_lock.wait()
+        for lock in self.sibling_locks:
+            lock.wait()
         self._run_task(t)
         if self.self_lock:
             self.self_lock.set()
 
-    def wait_for(self, _lock):
-        self.sibling_lock = _lock
+    def wait_for(self, siblings):
+        for sibling in siblings:
+            self.sibling_locks.append(sibling.get_lock())
 
     def name(self):
         return self.task