diff --git a/CHANGELOG b/CHANGELOG
index 4894c7b..3b05750 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -4,6 +4,9 @@ Format: Double ## for a version number followed by a space, ISO-Date, Semantic V
 Two empty lines before the next entry.
 External contributors notice at the end of the line: (LastName, FirstName / nick)
 
+## 2022-10-15 0.5.2
+Guard against crash/race condition where a note-off gui notification comes right after the instrument has been disabled
+Disable --mute for Tembro. We are sorry for the inconvenience.
 
 ## 2022-07-15 0.5.1
 Turn off auto connecting the mixer/auditioner audio ports when not run under NSM. Replace with default-off menu setting to do so.
diff --git a/qtgui/mainwindow.py b/qtgui/mainwindow.py
index 53a6da9..cae7221 100644
--- a/qtgui/mainwindow.py
+++ b/qtgui/mainwindow.py
@@ -18,11 +18,13 @@ GNU General Public License for more details.
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 """
-import logging; logging.info("import {}".format(__file__))
+
+import logging; logger = logging.getLogger(__name__); logger.info("import")
 
 #Standard Library Modules
 import pathlib
 import os
+import sys
 
 
 #Third Party Modules
@@ -45,6 +47,15 @@ from .verticalpiano import VerticalPiano
 from .horizontalpiano import HorizontalPiano
 from .chooseDownloadDirectory import ChooseDownloadDirectory
 
+#Template Modules
+from template.calfbox import cbox
+
+if "fake" in str(cbox):
+    logger.error("--mute is not supported in Tembro. We are sorry for the inconvenience.")
+    #We can quit here safely. Neither (fake) nsm nor anything related to audio is started.
+    sys.exit()
+
+
 class MainWindow(TemplateMainWindow):
 
     def __init__(self):