diff --git a/Lib/fontTools/subset.py b/Lib/fontTools/subset.py
index 273cd5a..b659800 100644
--- a/Lib/fontTools/subset.py
+++ b/Lib/fontTools/subset.py
@@ -1099,8 +1099,10 @@
       table.GlyphClassDef = None
   if table.AttachList:
     indices = table.AttachList.Coverage.subset(glyphs)
+    GlyphCount = table.AttachList.GlyphCount
     table.AttachList.AttachPoint = [table.AttachList.AttachPoint[i]
-                                    for i in indices]
+                                    for i in indices
+                                    if i < GlyphCount]
     table.AttachList.GlyphCount = len(table.AttachList.AttachPoint)
     if not table.AttachList.GlyphCount:
       table.AttachList = None