diff --git a/pyqtgraph/debug.py b/pyqtgraph/debug.py
index 4756423c..b59ee1a9 100644
--- a/pyqtgraph/debug.py
+++ b/pyqtgraph/debug.py
@@ -11,7 +11,7 @@ import sys, traceback, time, gc, re, types, weakref, inspect, os, cProfile, thre
 from . import ptime
 from numpy import ndarray
 from .Qt import QtCore, QtGui
-from .util.Mutex import Mutex
+from .util.mutex import Mutex
 from .util import cprint
 
 __ftraceDepth = 0
diff --git a/pyqtgraph/util/Mutex.py b/pyqtgraph/util/mutex.py
similarity index 100%
rename from pyqtgraph/util/Mutex.py
rename to pyqtgraph/util/mutex.py