diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 4fb028529b..fd06e6e568 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -1752,7 +1752,7 @@ class Formula
 
       popen_read_args = %w[]
       popen_read_args << commands
-      popen_read_args << shell_parameter unless shell_parameter.nil?
+      popen_read_args << shell_parameter unless shell_parameter.blank?
       popen_read_args.flatten!
 
       script_path.dirname.mkpath