diff --git a/lib/ecology.rb b/lib/ecology.rb
index e79e0d7..cd43e21 100644
--- a/lib/ecology.rb
+++ b/lib/ecology.rb
@@ -40,7 +40,7 @@ def read(ecology_pathname = nil)
       }
 
       if @ecology_initialized
-        if ecology_path != @ecology_path
+        if ecology_path != nil && ecology_path != @ecology_path
           raise "You've tried to load both #{ecology_path || "nothing"} and " +
             "#{@ecology_path || "nothing"} as ecology files since last reset!"
         end