diff --git a/stackrc b/stackrc
index ae87b22..cb9b817 100644
--- a/stackrc
+++ b/stackrc
@@ -101,12 +101,12 @@
 fi
 
 # Control whether Python 3 should be used.
-export USE_PYTHON3=${USE_PYTHON3:-False}
+export USE_PYTHON3=$(trueorfalse False USE_PYTHON3)
 
 # When Python 3 is supported by an application, adding the specific
 # version of Python 3 to this variable will install the app using that
 # version of the interpreter instead of 2.7.
-export PYTHON3_VERSION=${PYTHON3_VERSION:-3.4}
+export PYTHON3_VERSION=${PYTHON3_VERSION:-3.5}
 
 # Just to be more explicit on the Python 2 version to use.
 export PYTHON2_VERSION=${PYTHON2_VERSION:-2.7}