diff --git a/stdlib/printf.mli b/stdlib/printf.mli
index 739a474d2..a4d0ba989 100644
--- a/stdlib/printf.mli
+++ b/stdlib/printf.mli
@@ -66,12 +66,9 @@ val fprintf : out_channel -> ('a, out_channel, unit) format -> 'a
    - [t]: same as [%a], but takes only one argument (with type
      [out_channel -> unit]) and apply it to [outchan].
    - [\{ fmt %\}]: convert a format string argument to its minimal
-     specification. The argument must match the internal format string
-     specification [fmt] that enumerates the conversion specification
-     sequence that defines the format type of the argument.
-   - [\( fmt %\)]: printing format insertion. This convertion takes a
-     format string argument and substitutes it to the specification
-     [fmt] to print the following arguments.
+     specification. The argument must have the same type as [fmt].
+   - [\( fmt %\)]: printing format substitution. Use a format string
+     argument to replace [fmt]. The argument must have the same type as [fmt].
    - [!]: take no argument and flush the output.
    - [%]: take no argument and output one [%] character.
 
diff --git a/stdlib/scanf.mli b/stdlib/scanf.mli
index 7a2c65a2b..8f7d89cf2 100644
--- a/stdlib/scanf.mli
+++ b/stdlib/scanf.mli
@@ -150,17 +150,15 @@ val bscanf :
      first character of the range (or just after the [^] in case of
      range negation); hence [\[\]\]] matches a [\]] character and
      [\[^\]\]] matches any character that is not [\]].
-   - [\{ fmt %\}]: reads a format string that must have the same
-     type as the format string [fmt].
-     The argument is read according to the lexical conventions for
-     format strings described here.
+   - [\{ fmt %\}]: reads a format string argument to the format
+     specified by the internal format [fmt]. The format string to be
+     read must have the same type as the internal format [fmt].
      For instance, "%\{%i%\}" reads any format string that can read a value of
      type [int]; hence [Scanf.sscanf "fmt:\\\"number is %u\\\"" "fmt:%\{%i%\}"]
      succeeds and returns the format string ["number is %u"].
    - [\( fmt %\)]: scanning format substitution.
-     This conversion specifies a format string that should be read in the
-     input to replace [fmt]. The  format string read must have the same
-     type as [fmt].
+     Reads a format string to replace [fmt]. The format string read
+     must have the same type as [fmt].
    - [l]: applies [f] to the number of lines read so far.
    - [n]: applies [f] to the number of characters read so far.
    - [N] or [L]: applies [f] to the number of tokens read so far.