diff --git a/src/recipe.cr b/src/recipe.cr
index 2c15b26..1a89c86 100644
--- a/src/recipe.cr
+++ b/src/recipe.cr
@@ -144,7 +144,7 @@ class Package::Recipe
 						&.gsub(/^[ \t]*/, "").gsub(/[ \t]*$/, ""))
 
 					if match.size != 2
-						puts "WARNING: misformed option: #{option}"
+						STDERR.puts "WARNING: misformed option: #{option}"
 						next
 					end