diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 3d29321c78..c829fa3f3d 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -166,6 +166,7 @@ global table named like the mod.
 the table directly.
 * Use modern Minetest API
 * Tabs should be used for indent, spaces for alignment
+* Use double quotes for strings
 
 ### Changes to Gameplay
 Pull Requests that change gameplay have to be properly researched and