diff --git a/FlatCAMApp.py b/FlatCAMApp.py
index 226362ca..82574b1a 100644
--- a/FlatCAMApp.py
+++ b/FlatCAMApp.py
@@ -259,14 +259,15 @@ class App(QtCore.QObject):
         # Setup the listening thread for another instance launching with args #####
         # #########################################################################
 
-        # make sure the thread is stored by using a self. otherwise it's garbage collected
-        self.th = QtCore.QThread()
-        self.th.start(priority=QtCore.QThread.LowestPriority)
+        if sys.platform == 'win32' or sys.platform == 'linux':
+            # make sure the thread is stored by using a self. otherwise it's garbage collected
+            self.th = QtCore.QThread()
+            self.th.start(priority=QtCore.QThread.LowestPriority)
 
-        self.new_launch = ArgsThread()
-        self.new_launch.open_signal[list].connect(self.on_startup_args)
-        self.new_launch.moveToThread(self.th)
-        self.new_launch.start.emit()
+            self.new_launch = ArgsThread()
+            self.new_launch.open_signal[list].connect(self.on_startup_args)
+            self.new_launch.moveToThread(self.th)
+            self.new_launch.start.emit()
 
         # ############################################################################
         # # ################# OS-specific ############################################
diff --git a/README.md b/README.md
index 8234df23..b4d6ad46 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,7 @@ CAD program, and create G-Code for Isolation routing.
 
 - started to rework the NCC Tool GUI in preparation for adding a Tool DB feature
 - for auto-completer, now clicking an entry in the completer popup will select that entry and insert it
+- made available only for Linux and Windows (not OSX) the starting of the thread that checks if another instance of FlatCAM is already running at the launch of FLatCAM
 
 1.01.2020
 
diff --git a/share/dark_resources/makearea32.png b/share/dark_resources/markarea32.png
similarity index 100%
rename from share/dark_resources/makearea32.png
rename to share/dark_resources/markarea32.png