diff --git a/doc/client_lua_api.txt b/doc/client_lua_api.txt
index 36eeafcf1..098596481 100644
--- a/doc/client_lua_api.txt
+++ b/doc/client_lua_api.txt
@@ -620,7 +620,7 @@ Helper functions
 * `minetest.is_yes(arg)`
     * returns whether `arg` can be interpreted as yes
 * `minetest.is_nan(arg)`
-    * returns true true when the passed number represents NaN.
+    * returns true when the passed number represents NaN.
 * `table.copy(table)`: returns a table
     * returns a deep copy of `table`