diff --git a/docs/fileformats.html b/docs/fileformats.html
index 8f36120d730..368aafe0bdf 100644
--- a/docs/fileformats.html
+++ b/docs/fileformats.html
@@ -1077,10 +1077,10 @@ limitations under the License.
                     segment.
                 </p>
                                                 <p>
-                    Segments    --&gt; Format, Version, SegCount, &lt;SegName, SegSize&gt;<sup>SegCount</sup>
+                    Segments    --&gt; Format, Version, NameCounter, SegCount, &lt;SegName, SegSize&gt;<sup>SegCount</sup>
                 </p>
                                                 <p>
-                    Format, SegCount, SegSize    --&gt; UInt32
+                    Format, NameCounter, SegCount, SegSize    --&gt; UInt32
                 </p>
                                                 <p>
                     Version --&gt; UInt64
@@ -1094,6 +1094,9 @@ limitations under the License.
                                                 <p>
                     Version counts how often the index has been
                     changed by adding or deleting documents.
+                </p>
+                                                <p>
+                    NameCounter is used to generate names for new segment files.
                 </p>
                                                 <p>
                     SegName is the name of the segment, and is used as the file name prefix
diff --git a/xdocs/fileformats.xml b/xdocs/fileformats.xml
index 8654c399094..ce035178d44 100644
--- a/xdocs/fileformats.xml
+++ b/xdocs/fileformats.xml
@@ -698,11 +698,11 @@
                 </p>
 
                 <p>
-                    Segments    --&gt; Format, Version, SegCount, &lt;SegName, SegSize&gt;<sup>SegCount</sup>
+                    Segments    --&gt; Format, Version, NameCounter, SegCount, &lt;SegName, SegSize&gt;<sup>SegCount</sup>
                 </p>
 
                 <p>
-                    Format, SegCount, SegSize    --&gt; UInt32
+                    Format, NameCounter, SegCount, SegSize    --&gt; UInt32
                 </p>
 
                 <p>
@@ -722,6 +722,10 @@
                     changed by adding or deleting documents.
                 </p>
 
+                <p>
+                    NameCounter is used to generate names for new segment files.
+                </p>
+
                 <p>
                     SegName is the name of the segment, and is used as the file name prefix
                     for all of the files that compose the segment's index.