diff --git a/desmod/pool.py b/desmod/pool.py
index 58f53ec5..ff3f8723 100644
--- a/desmod/pool.py
+++ b/desmod/pool.py
@@ -13,6 +13,8 @@
 class PoolPutEvent(Event):
     def __init__(self, pool, amount=1):
         super(PoolPutEvent, self).__init__(pool.env)
+        if amount <= 0:
+            raise ValueError('amount {} must be > 0'.format(amount))
         self.pool = pool
         self.amount = amount
         self.callbacks.append(pool._trigger_get)
@@ -28,6 +30,11 @@ def cancel(self):
 class PoolGetEvent(Event):
     def __init__(self, pool, amount=1):
         super(PoolGetEvent, self).__init__(pool.env)
+        if amount <= 0:
+            raise ValueError('amount {} must be > 0'.format(amount))
+        assert amount <= pool.capacity, (
+            "Amount {} greater than pool's {} capacity {}".format(
+                amount, str(pool.name), pool.capacity))
         self.pool = pool
         self.amount = amount
         self.callbacks.append(pool._trigger_put)
@@ -97,13 +104,13 @@ class Pool(object):
 
     """
 
-    def __init__(self, env, capacity=float('inf'), hard_cap=False,
-                 init_level=0, name=None):
+    def __init__(self, env, capacity=float('inf'), init=0, hard_cap=False,
+                 name=None):
         self.env = env
         #: Capacity of the queue (maximum number of items).
         self.capacity = capacity
         self._hard_cap = hard_cap
-        self.level = init_level
+        self.level = init
         self.name = name
         self._putters = []
         self._getters = []
@@ -149,8 +156,7 @@ def _trigger_put(self, _=None):
             put_ev = self._putters.pop(0)
             put_ev.succeed()
             self.level += put_ev.amount
-            if put_ev.amount:
-                self._trigger_when_new()
+            self._trigger_when_new()
             self._trigger_when_any()
             self._trigger_when_full()
             if self._put_hook:
@@ -159,19 +165,16 @@ def _trigger_put(self, _=None):
             raise OverflowError()
 
     def _trigger_get(self, _=None):
-        if self._getters and self.level:
-            for get_ev in self._getters:
-                assert get_ev.amount <= self.capacity, (
-                    "Amount {} greater than pool's {} capacity {}".format(
-                        get_ev.amount, str(self.name), self.capacity))
-                if get_ev.amount <= self.level:
-                    self._getters.remove(get_ev)
-                    self.level -= get_ev.amount
-                    get_ev.succeed(get_ev.amount)
-                    if self._get_hook:
-                        self._get_hook()
-                else:
-                    break
+        while self._getters and self.level:
+            get_ev = self._getters[0]
+            if get_ev.amount <= self.level:
+                assert self._getters.pop(0) is get_ev
+                self.level -= get_ev.amount
+                get_ev.succeed(get_ev.amount)
+                if self._get_hook:
+                    self._get_hook()
+            else:
+                break
 
     def _trigger_when_new(self):
         for when_new_ev in self._new_waiters:
diff --git a/tests/test_pool.py b/tests/test_pool.py
index b2852552..7134de39 100644
--- a/tests/test_pool.py
+++ b/tests/test_pool.py
@@ -78,7 +78,7 @@ def test_pool_overflow(env):
 
     def producer(env):
         yield env.timeout(1)
-        for i in range(5):
+        for i in range(1, 5):
             yield pool.put(i)
             yield env.timeout(1)
 
@@ -87,6 +87,28 @@ def producer(env):
         env.run()
 
 
+def test_pool_put_zero(env):
+    pool = Pool(env, capacity=5, hard_cap=True)
+
+    def producer(env):
+        yield pool.put(0)
+
+    env.process(producer(env))
+    with raises(ValueError):
+        env.run()
+
+
+def test_pool_get_zero(env):
+    pool = Pool(env, capacity=5, hard_cap=True)
+
+    def consumer(env):
+        yield pool.get(0)
+
+    env.process(consumer(env))
+    with raises(ValueError):
+        env.run()
+
+
 def test_pool_get_more(env):
     pool = Pool(env, capacity=6, name='foo')