diff --git a/Library/Homebrew/utils/curl.rb b/Library/Homebrew/utils/curl.rb
index 37a4f71e4f..1bfb499727 100644
--- a/Library/Homebrew/utils/curl.rb
+++ b/Library/Homebrew/utils/curl.rb
@@ -305,7 +305,7 @@ module Utils
       file = Tempfile.new.tap(&:close)
 
       specs = specs.flat_map do |option, argument|
-        next if argument == false # No flag.
+        next [] if argument == false # No flag.
 
         args = ["--#{option.to_s.tr("_", "-")}"]
         args << argument unless argument == true # It's a flag.