diff --git a/bugsink/period_counter.py b/bugsink/period_counter.py
index 1ac74d5..751020c 100644
--- a/bugsink/period_counter.py
+++ b/bugsink/period_counter.py
@@ -99,18 +99,18 @@ class PeriodCounter(object):
                         wbt()
 
     def add_event_listener(self, period_name, how_many_periods, gte_threshold, when_becomes_true, when_becomes_false,
-                           event_state=None, tup=None):
+                           initial_event_state=None, tup=None):
 
-        if len([arg for arg in [event_state, tup] if arg is None]) != 1:
+        if len([arg for arg in [initial_event_state, tup] if arg is None]) != 1:
             # either be explicit, or let us deduce
-            raise ValueError("Provide exactly one of (event_state, tup)")
+            raise ValueError("Provide exactly one of (initial_event_state, tup)")
 
         tl = self._tl_for_period(period_name)
-        if event_state is None:
-            event_state = self._get_event_state(tup, tl, how_many_periods, gte_threshold)
+        if initial_event_state is None:
+            initial_event_state = self._get_event_state(tup, tl, how_many_periods, gte_threshold)
 
         self.event_listeners[tl][(how_many_periods, gte_threshold)] = \
-            (when_becomes_true, when_becomes_false, event_state)
+            (when_becomes_true, when_becomes_false, initial_event_state)
 
     def _tl_for_period(self, period_name):
         return {
diff --git a/bugsink/tests.py b/bugsink/tests.py
index 25d3163..79cc715 100644
--- a/bugsink/tests.py
+++ b/bugsink/tests.py
@@ -57,7 +57,7 @@ class PeriodCounterTestCase(TestCase):
         pc = PeriodCounter()
         wbt = callback()
         wbf = callback()
-        pc.add_event_listener("total", 1, 2, wbt, wbf, event_state=False)
+        pc.add_event_listener("total", 1, 2, wbt, wbf, initial_event_state=False)
 
         # first inc: should not yet trigger
         pc.inc(timepoint)
@@ -79,7 +79,7 @@ class PeriodCounterTestCase(TestCase):
         pc = PeriodCounter()
         wbt = callback()
         wbf = callback()
-        pc.add_event_listener("year", 2, 3, wbt, wbf, event_state=False)
+        pc.add_event_listener("year", 2, 3, wbt, wbf, initial_event_state=False)
 
         pc.inc(tp_2020)
         self.assertEquals(0, wbt.calls)
diff --git a/performance/some_script.py b/performance/some_script.py
index 036bd4b..4709fca 100644
--- a/performance/some_script.py
+++ b/performance/some_script.py
@@ -77,9 +77,9 @@ def print_thoughts_about_event_evaluation():
     # Project. In this setup, the monthly maximum is spread out in a way that the smaller parts are a bit more than just
     # splitting things equally. Why? We want some flexibility for bursts of activity without using up the entire budget
     # for a longer time all at once.
-    pc.add_event_listener("day",    30, 10_000, noop, noop, event_state=False)  # 1 month rolling window
-    pc.add_event_listener("hour",   24,  1_000, noop, noop, event_state=False)  # 1 day rolling window
-    pc.add_event_listener("minute", 60,    200, noop, noop, event_state=False)  # 1 hour rolling window
+    pc.add_event_listener("day",    30, 10_000, noop, noop, initial_event_state=False)  # 1 month rolling window
+    pc.add_event_listener("hour",   24,  1_000, noop, noop, initial_event_state=False)  # 1 day rolling window
+    pc.add_event_listener("minute", 60,    200, noop, noop, initial_event_state=False)  # 1 hour rolling window
 
     # make sure the pc has some data before we start. we pick a 1-month period to match the listeners in the above.
     for point in buckets_to_points_in_time(