Index: ghc-8.6.1/libraries/containers/include/containers.h
===================================================================
--- ghc-8.6.1.orig/libraries/containers/include/containers.h
+++ ghc-8.6.1/libraries/containers/include/containers.h
@@ -35,7 +35,6 @@
 
 #ifdef __GLASGOW_HASKELL__
 # define USE_ST_MONAD 1
-# define USE_UNBOXED_ARRAYS 1
 #endif
 
 #endif