diff --git a/reference/readline/functions/readline-callback-handler-install.xml b/reference/readline/functions/readline-callback-handler-install.xml
index d1ae71772a8e..18d45650fe27 100644
--- a/reference/readline/functions/readline-callback-handler-install.xml
+++ b/reference/readline/functions/readline-callback-handler-install.xml
@@ -25,6 +25,10 @@
    <function>stream_select</function> as it allows interleaving of IO and
    user input, unlike <function>readline</function>.
   </para>
+  <para>
+   This function is unavailable on Windows and other systems that do not support
+   the readline callback feature.
+  </para>
  </refsect1>
 
  <refsect1 role="parameters">
diff --git a/reference/readline/functions/readline-callback-handler-remove.xml b/reference/readline/functions/readline-callback-handler-remove.xml
index c7c328ba758a..9f331b88a2db 100644
--- a/reference/readline/functions/readline-callback-handler-remove.xml
+++ b/reference/readline/functions/readline-callback-handler-remove.xml
@@ -16,6 +16,10 @@
    Removes a previously installed callback handler and restores terminal
    settings.
   </para>
+  <para>
+   This function is unavailable on Windows and other systems that do not support
+   the readline callback feature.
+  </para>
  </refsect1>
 
  <refsect1 role="parameters">
diff --git a/reference/readline/functions/readline-callback-read-char.xml b/reference/readline/functions/readline-callback-read-char.xml
index bec5b46d24b3..9657296bee09 100644
--- a/reference/readline/functions/readline-callback-read-char.xml
+++ b/reference/readline/functions/readline-callback-read-char.xml
@@ -18,6 +18,10 @@
    <function>readline_callback_handler_install</function> that a line
    is ready for input.
   </para>
+  <para>
+   This function is unavailable on Windows and other systems that do not support
+   the readline callback feature.
+  </para>
  </refsect1>
 
  <refsect1 role="parameters">
diff --git a/reference/readline/functions/readline-list-history.xml b/reference/readline/functions/readline-list-history.xml
index 4960fb7d640b..cfe99fa945fc 100644
--- a/reference/readline/functions/readline-list-history.xml
+++ b/reference/readline/functions/readline-list-history.xml
@@ -15,6 +15,10 @@
   <para>
    Gets the entire command line history.
   </para>
+  <para>
+   This function is unavailable if this feature is not supported by readline on
+   your system.
+  </para>
  </refsect1>
 
  <refsect1 role="parameters">
diff --git a/reference/readline/functions/readline-on-new-line.xml b/reference/readline/functions/readline-on-new-line.xml
index 7c588428fd4c..3924a463474d 100644
--- a/reference/readline/functions/readline-on-new-line.xml
+++ b/reference/readline/functions/readline-on-new-line.xml
@@ -15,6 +15,10 @@
   <para>
    Tells readline that the cursor has moved to a new line.
   </para>
+  <para>
+   This function is unavailable on Windows and other systems that do not support
+   the readline callback feature.
+  </para>
  </refsect1>
 
  <refsect1 role="parameters">
diff --git a/reference/readline/functions/readline-redisplay.xml b/reference/readline/functions/readline-redisplay.xml
index 90dcd13af0a3..8cb67324c485 100644
--- a/reference/readline/functions/readline-redisplay.xml
+++ b/reference/readline/functions/readline-redisplay.xml
@@ -15,6 +15,10 @@
   <para>
    Redraws readline to redraw the display.
   </para>
+  <para>
+   This function is unavailable on Windows and other systems that do not support
+   the readline callback feature.
+  </para>
  </refsect1>
 
  <refsect1 role="parameters">