--- a/rakelib/compile.rake	Sat Dec 17 22:22:43 2016 +0000
+++ b/rakelib/compile.rake	Tue Dec 20 17:50:14 2016 +0000
@@ -23,7 +23,7 @@
 # avoid sources to leak (for exaple, due to a bug in packaging scripts).
 # Unathorized subjects should not be able to checkout sources in first instance.
 def should_remove_librun_and_stc_sources
-    return ! (core_developer? or ENV['RETAIN_STX_AND_LIBRUN_SOURCE'] = 'yespleaseretain!')
+    return ! (core_developer? or ENV['RETAIN_STX_AND_LIBRUN_SOURCE'] == 'yespleaseretain!')
 end
 
 def rm_rf_all_in_except(directory, exceptions = [])