diff --git a/stack.yaml b/stack.yaml
index 0d77c2ec7..a8f5ffcbb 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -4,6 +4,7 @@ resolver: nightly-2017-12-05
 
 nix:
   enable: false
+  pure: false
   packages: [perl gmp ncurses zlib]
 
 # extra-deps: