diff --git a/mk/config.mk.in b/mk/config.mk.in
index c9b1d6c8f4d430cfa397214048b7903d38eac3d6..14195e9a0969280a54f1e1610317459d6dcf4303 100644
--- a/mk/config.mk.in
+++ b/mk/config.mk.in
@@ -355,10 +355,10 @@ NoFibSubDirs = imaginary spectral real
 # The different ways to build nofib. Default is just to mirror
 # what is done for the ghc prelude libraries.
 #
-NoFibWays=$(GhcLibWays)
+NoFibWays = $(GhcLibWays)
 
 # Haskell compiler options for nofib
-NoFibHcOpts=
+NoFibHcOpts = -O
 
 # ==============================================================================
 #