diff --git a/lix/libexpr/builtins/toString.md b/lix/libexpr/builtins/toString.md
index 1db5cd91a..bdc009f13 100644
--- a/lix/libexpr/builtins/toString.md
+++ b/lix/libexpr/builtins/toString.md
@@ -13,6 +13,8 @@ Convert the expression *e* to a string. *e* can be:
 
   - An integer.
 
+  - A floating-point value, it will be converted to the decimal notation in the style `[-]ddd.ddd` with 6 digits appearing after the decimal point.
+
   - A list, in which case the string representations of its elements
     are joined with spaces.