1 files changed, 12 insertions, 1 deletions
diff --git a/Tools/build/freeze_modules.py b/Tools/build/freeze_modules.py
index c5a3971..6a54f45 100644
--- a/Tools/build/freeze_modules.py
+++ b/Tools/build/freeze_modules.py
@@ -468,6 +468,17 @@ def replace_block(lines, start_marker, end_marker, replacements, file):
     return lines[:start_pos + 1] + replacements + lines[end_pos:]
 
 
+class UniqueList(list):
+    def __init__(self):
+        self._seen = set()
+
+    def append(self, item):
+        if item in self._seen:
+            return
+        super().append(item)
+        self._seen.add(item)
+
+
 def regen_frozen(modules):
     headerlines = []
     parentdir = os.path.dirname(FROZEN_FILE)
@@ -477,7 +488,7 @@ def regen_frozen(modules):
         header = relpath_for_posix_display(src.frozenfile, parentdir)
         headerlines.append(f'#include "{header}"')
 
-    externlines = []
+    externlines = UniqueList()
     bootstraplines = []
     stdliblines = []
     testlines = []