diff --git a/appendices/ini.core.xml b/appendices/ini.core.xml
index f2b3d426e2..baf79b13f2 100644
--- a/appendices/ini.core.xml
+++ b/appendices/ini.core.xml
@@ -243,6 +243,8 @@
       <listitem>
        <simpara>
         The number of significant digits displayed in floating point numbers.
+        <literal>-1</literal> means that an enhanced algorithm for rounding 
+        such numbers will be used.
        </simpara>
       </listitem>
      </varlistentry>
@@ -255,7 +257,9 @@
       <listitem>
        <simpara>
         The number of significant digits stored while serializing floating point numbers.
-       </simpara>
+        <literal>-1</literal> means that an enhanced algorithm for rounding 
+        such numbers will be used.
+      </simpara>
       </listitem>
      </varlistentry>
      
diff --git a/appendices/ini.list.xml b/appendices/ini.list.xml
index dd62cd94b2..c586254fd6 100644
--- a/appendices/ini.list.xml
+++ b/appendices/ini.list.xml
@@ -2349,10 +2349,11 @@
       </row>
       <row>
        <entry><link linkend="ini.serialize-precision">serialize_precision</link></entry>
-       <entry>"17"</entry>
+       <entry>"-1"</entry>
        <entry>PHP_INI_ALL</entry>
        <entry>
         Available since PHP 4.3.2. Until PHP 5.3.5, the default value was 100.
+        Until PHP 7.1.0, the default value was 17.
        </entry>
       </row>
       <row>