diff --git a/Lib/lib-tk/FixTk.py b/Lib/lib-tk/FixTk.py
index c0af29b..029e7cd 100644
--- a/Lib/lib-tk/FixTk.py
+++ b/Lib/lib-tk/FixTk.py
@@ -1,6 +1,11 @@
 import sys, os, _tkinter
+
 ver = str(_tkinter.TCL_VERSION)
-for t in "tcl", "tk":
-    v = os.path.join(sys.prefix, "tcl", t+ver)
-    if os.path.exists(os.path.join(v, "tclIndex")):
-        os.environ[t.upper() + "_LIBRARY"] = v
+for t in "tcl", "tk", "tix":
+    key = t.upper() + "_LIBRARY"
+    try:
+        v = os.environ[key]
+    except KeyError:
+        v = os.path.join(sys.prefix, "tcl", t+ver)
+        if os.path.exists(os.path.join(v, "tclIndex")):
+            os.environ[key] = v