diff --git a/reference/image/functions/imagettfbbox.xml b/reference/image/functions/imagettfbbox.xml
index 40dbae2e36..b7b4317985 100644
--- a/reference/image/functions/imagettfbbox.xml
+++ b/reference/image/functions/imagettfbbox.xml
@@ -67,9 +67,15 @@
   <para>
    <function>imagettfbbox</function> returns an array with 8
    elements representing four points making the bounding box of the
-   text:
+   text on success and &false; on error.
    <informaltable>
     <tgroup cols="2">
+     <thead>
+      <row>
+       <entry>key</entry>
+       <entry>contents</entry>
+      </row>
+     </thead>
      <tbody>
       <row>
        <entry>0</entry>