diff --git a/lib/vmfloaty/pooler.rb b/lib/vmfloaty/pooler.rb
index 8bdef2c..539e85b 100644
--- a/lib/vmfloaty/pooler.rb
+++ b/lib/vmfloaty/pooler.rb
@@ -46,7 +46,7 @@ class Pooler
 
     os_string = os_string.chomp('+')
 
-    if os_string.size == 0
+    if os_string.empty?
       raise MissingParamError, 'No operating systems provided to obtain.'
     end