diff --git a/Lib/fontTools/cffLib/CFF2ToCFF.py b/Lib/fontTools/cffLib/CFF2ToCFF.py
index 744621fd9..aacbf8efc 100644
--- a/Lib/fontTools/cffLib/CFF2ToCFF.py
+++ b/Lib/fontTools/cffLib/CFF2ToCFF.py
@@ -19,7 +19,7 @@ def convertCFF2ToCFF(cff, otFont):
     default instance?)
 
     This assumes a decompiled CFF table. (i.e. that the object has been
-    filled via :meth:`decompile`.)"""
+    filled via :meth:`decompile` and e.g. not loaded from XML.)"""
 
     cff.major = 1
     topDict = cff.topDictIndex[0]
diff --git a/Lib/fontTools/cffLib/CFFToCFF2.py b/Lib/fontTools/cffLib/CFFToCFF2.py
index abdf7e7a1..d14b35e9c 100644
--- a/Lib/fontTools/cffLib/CFFToCFF2.py
+++ b/Lib/fontTools/cffLib/CFFToCFF2.py
@@ -23,7 +23,7 @@ def convertCFFToCFF2(cff, otFont):
     is done 'in-place'. The conversion cannot be reversed.
 
     This assumes a decompiled CFF table. (i.e. that the object has been
-    filled via :meth:`decompile`.)"""
+    filled via :meth:`decompile` and e.g. not loaded from XML.)"""
 
     cff.major = 2
     cff2GetGlyphOrder = cff.otFont.getGlyphOrder