diff --git a/functions/image.xml b/functions/image.xml
index b88667c233..14aa480869 100644
--- a/functions/image.xml
+++ b/functions/image.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.63 $ -->
+<!-- $Revision: 1.64 $ -->
 <reference id="ref.image">
  <title>Image functions</title>
  <titleabbrev>Image</titleabbrev>
@@ -460,6 +460,9 @@ $black = ImageColorAllocate ($im, 0, 0, 0);
      </programlisting>
     </informalexample>
    </para>
+   <para>
+    Returns -1 if the allocation failed.
+   </para>
   </refsect1>
  </refentry>