diff -r 69d0c4bbdf2f rpython/rtyper/lltypesystem/rffi.py
--- a/rpython/rtyper/lltypesystem/rffi.py       Tue Jul 23 06:50:41 2019 +0200
+++ b/rpython/rtyper/lltypesystem/rffi.py       Wed Jul 24 09:16:48 2019 +0200
@@ -868,6 +868,8 @@
                 flag = '\x05'     # successfully pinned
             else:
                 flag = '\x06'     # must still make a copy
+        from rpython.rlib.debug import debug_print
+        debug_print("get_nonmovingbuffer: flag =", ord(flag))
         if flag == '\x06':
             buf = lltype.malloc(TYPEP.TO, count + (TYPEP is CCHARP),
                                 flavor='raw')
@@ -905,6 +907,8 @@
         Keep 'data' alive and unpin it if it was pinned (flag==\5).
         Otherwise free the non-moving copy (flag==\6).
         """
+        from rpython.rlib.debug import debug_print
+        debug_print("free_nonmovingbuffer: flag =", ord(flag))
         if flag == '\x05':
             rgc.unpin(data)
         if flag == '\x06':