diff --git a/stackrc b/stackrc
index e76abc0..c59d0a4 100644
--- a/stackrc
+++ b/stackrc
@@ -154,7 +154,7 @@
 #
 # - True : use upper-constraints.txt to constrain versions of packages intalled
 #          and do not edit projects at all.
-USE_CONSTRAINTS=${USE_CONSTRAINTS:-False}
+USE_CONSTRAINTS=$(trueorfalse False USE_CONSTRAINTS)
 
 # Repositories
 # ------------