diff --git a/generic/tclClock.c b/generic/tclClock.c
index 980ff1b..113a5d2 100644
--- a/generic/tclClock.c
+++ b/generic/tclClock.c
@@ -4731,6 +4731,8 @@ ClockFinalize(
     if (tzWas && tzWas != INT2PTR(-1)) {
 	ckfree(tzWas);
     }
+
+    Tcl_MutexFinalize(&clockMutex);
 }
 
 /*