diff --git a/base/qt/app.py b/base/qt/app.py
index 83fbd849..b710c9c5 100644
--- a/base/qt/app.py
+++ b/base/qt/app.py
@@ -159,8 +159,8 @@ class DupeGuru(DupeGuruBase, QObject):
             self.add_to_ignore_list(dupe)
         self.remove_duplicates(duplicates)
     
-    def ApplyFilter(self, filter):
-        DupeGuruBase.ApplyFilter(self, filter)
+    def apply_filter(self, filter):
+        DupeGuruBase.apply_filter(self, filter)
         self.emit(SIGNAL('resultsChanged()'))
     
     def ask_for_reg_code(self):
diff --git a/base/qt/main_window.py b/base/qt/main_window.py
index 3ca20de3..1f93d0f2 100644
--- a/base/qt/main_window.py
+++ b/base/qt/main_window.py
@@ -156,11 +156,11 @@ class MainWindow(QMainWindow, Ui_MainWindow):
         if not ok:
             return
         answer = unicode(answer)
-        self.app.ApplyFilter(answer)
+        self.app.apply_filter(answer)
         self._last_filter = answer
     
     def cancelFilterTriggered(self):
-        self.app.ApplyFilter('')
+        self.app.apply_filter('')
     
     def checkForUpdateTriggered(self):
         QProcess.execute('updater.exe', ['/checknow'])
diff --git a/me/cocoa/py/dg_cocoa.py b/me/cocoa/py/dg_cocoa.py
index 313b196b..b10b725a 100644
--- a/me/cocoa/py/dg_cocoa.py
+++ b/me/cocoa/py/dg_cocoa.py
@@ -80,7 +80,7 @@ class PyDupeGuru(PyApp):
         self.app.AddSelectedToIgnoreList()
     
     def applyFilter_(self, filter):
-        self.app.ApplyFilter(filter)
+        self.app.apply_filter(filter)
     
     def deleteMarked(self):
         self.app.delete_marked()
diff --git a/pe/cocoa/py/dg_cocoa.py b/pe/cocoa/py/dg_cocoa.py
index 45a09cf3..f74a4f7a 100644
--- a/pe/cocoa/py/dg_cocoa.py
+++ b/pe/cocoa/py/dg_cocoa.py
@@ -85,7 +85,7 @@ class PyDupeGuru(PyApp):
         self.app.delete_marked()
     
     def applyFilter_(self, filter):
-        self.app.ApplyFilter(filter)
+        self.app.apply_filter(filter)
     
     def makeSelectedReference(self):
         self.app.MakeSelectedReference()
diff --git a/py/app.py b/py/app.py
index 1c3e24a4..276a879c 100644
--- a/py/app.py
+++ b/py/app.py
@@ -119,7 +119,7 @@ class DupeGuru(RegistrableApplication):
             if other is not dupe:
                 self.scanner.ignore_list.Ignore(unicode(other.path), unicode(dupe.path))
     
-    def ApplyFilter(self, filter):
+    def apply_filter(self, filter):
         self.results.apply_filter(None)
         if self.options['escape_filter_regexp']:
             filter = escape(filter, '()[]\\.|+?^')
diff --git a/py/app_test.py b/py/app_test.py
index af47067f..9cd732d3 100644
--- a/py/app_test.py
+++ b/py/app_test.py
@@ -33,27 +33,27 @@ class DupeGuru(DupeGuruBase):
 
 class TCDupeGuru(TestCase):
     cls_tested_module = app
-    def test_ApplyFilter_calls_results_apply_filter(self):
+    def test_apply_filter_calls_results_apply_filter(self):
         app = DupeGuru()
         self.mock(app.results, 'apply_filter', log_calls(app.results.apply_filter))
-        app.ApplyFilter('foo')
+        app.apply_filter('foo')
         self.assertEqual(2, len(app.results.apply_filter.calls))
         call = app.results.apply_filter.calls[0]
         self.assert_(call['filter_str'] is None)
         call = app.results.apply_filter.calls[1]
         self.assertEqual('foo', call['filter_str'])
     
-    def test_ApplyFilter_escapes_regexp(self):
+    def test_apply_filter_escapes_regexp(self):
         app = DupeGuru()
         self.mock(app.results, 'apply_filter', log_calls(app.results.apply_filter))
-        app.ApplyFilter('()[]\\.|+?^abc')
+        app.apply_filter('()[]\\.|+?^abc')
         call = app.results.apply_filter.calls[1]
         self.assertEqual('\\(\\)\\[\\]\\\\\\.\\|\\+\\?\\^abc', call['filter_str'])
-        app.ApplyFilter('(*)') # In "simple mode", we want the * to behave as a wilcard
+        app.apply_filter('(*)') # In "simple mode", we want the * to behave as a wilcard
         call = app.results.apply_filter.calls[3]
         self.assertEqual('\(.*\)', call['filter_str'])
         app.options['escape_filter_regexp'] = False
-        app.ApplyFilter('(abc)')
+        app.apply_filter('(abc)')
         call = app.results.apply_filter.calls[5]
         self.assertEqual('(abc)', call['filter_str'])
     
diff --git a/se/cocoa/py/dg_cocoa.py b/se/cocoa/py/dg_cocoa.py
index 2d465c94..f9d73d27 100644
--- a/se/cocoa/py/dg_cocoa.py
+++ b/se/cocoa/py/dg_cocoa.py
@@ -82,7 +82,7 @@ class PyDupeGuru(PyApp):
         self.app.delete_marked()
     
     def applyFilter_(self, filter):
-        self.app.ApplyFilter(filter)
+        self.app.apply_filter(filter)
     
     def makeSelectedReference(self):
         self.app.MakeSelectedReference()