diff --git a/Lib/fontTools/subset/__init__.py b/Lib/fontTools/subset/__init__.py
index d45556bb1..6e17cc33e 100644
--- a/Lib/fontTools/subset/__init__.py
+++ b/Lib/fontTools/subset/__init__.py
@@ -1798,17 +1798,20 @@ def subset_glyphs(self, s):
 	used = set()
 
 	if table.AdvWidthMap:
-		table.AdvWidthMap.mapping = _dict_subset(table.AdvWidthMap.mapping, s.glyphs)
+		if not s.options.retain_gids:
+			table.AdvWidthMap.mapping = _dict_subset(table.AdvWidthMap.mapping, s.glyphs)
 		used.update(table.AdvWidthMap.mapping.values())
 	else:
 		assert table.LsbMap is None and table.RsbMap is None, "File a bug."
 		used.update(s.reverseOrigGlyphMap.values())
 
 	if table.LsbMap:
-		table.LsbMap.mapping = _dict_subset(table.LsbMap.mapping, s.glyphs)
+		if not s.options.retain_gids:
+			table.LsbMap.mapping = _dict_subset(table.LsbMap.mapping, s.glyphs)
 		used.update(table.LsbMap.mapping.values())
 	if table.RsbMap:
-		table.RsbMap.mapping = _dict_subset(table.RsbMap.mapping, s.glyphs)
+		if not s.options.retain_gids:
+			table.RsbMap.mapping = _dict_subset(table.RsbMap.mapping, s.glyphs)
 		used.update(table.RsbMap.mapping.values())
 
 	varidx_map = varStore.VarStore_subset_varidxes(table.VarStore, used)