diff -r 110e3c57792a rpython/memory/gctypelayout.py
--- a/rpython/memory/gctypelayout.py	Wed Feb 07 09:39:56 2018 -0500
+++ b/rpython/memory/gctypelayout.py	Wed Feb 07 12:01:23 2018 -0500
@@ -241,10 +241,10 @@
         infobits |= T_HAS_GCPTR
     #
     fptrs = builder.special_funcptr_for_type(TYPE)
+    customdata = lltype.malloc(GCData.CUSTOM_DATA_STRUCT, flavor='raw',
+                               immortal=True)
+    info.customdata = customdata
     if fptrs or has_special_memory_pressure(TYPE):
-        customdata = lltype.malloc(GCData.CUSTOM_DATA_STRUCT, flavor='raw',
-                                   immortal=True)
-        info.customdata = customdata
         if "destructor" in fptrs:
             customdata.customfunc = fptrs["destructor"]
         if "old_style_finalizer" in fptrs: