diff --git a/Contributing.asciidoc b/Contributing.asciidoc
index 6b9779c51..4991933e1 100644
--- a/Contributing.asciidoc
+++ b/Contributing.asciidoc
@@ -9,6 +9,8 @@
 First, some basic things:
 
 * Use only English to communicate with developers.
+* Search in issues if the same problem or feature request has already been
+  reported (a duplicate is waste of time for you and the developers!).
 * If you can, please check if the problem has been fixed in development version
   (if you are using a stable release or old version).
 * Report only one bug or feature request per issue.