diff --git a/stackrc b/stackrc
index c81906a..8b97536 100644
--- a/stackrc
+++ b/stackrc
@@ -275,6 +275,9 @@
 # Set default screen name
 SCREEN_NAME=${SCREEN_NAME:-stack}
 
+# Do not install packages tagged with 'testonly' by default
+INSTALL_TESTONLY_PACKAGES=${INSTALL_TESTONLY_PACKAGES:-False}
+
 # Local variables:
 # mode: shell-script
 # End: