--- libraries/base/base.cabal.orig	2021-06-05 13:37:03 UTC
+++ libraries/base/base.cabal
@@ -404,6 +404,9 @@ Library
             System.CPUTime.Posix.RUsage
             System.CPUTime.Unsupported
 
+    if os(freebsd)
+        cc-options: -DLIBICONV_PLUG
+
     -- We need to set the unit id to base (without a version number)
     -- as it's magic.
     ghc-options: -this-unit-id base