diff --git a/cave_data/2010-04.html b/cave_data/1623-2010-04.html
similarity index 92%
rename from cave_data/2010-04.html
rename to cave_data/1623-2010-04.html
index 88f105893..3d1260e3f 100644
--- a/cave_data/2010-04.html
+++ b/cave_data/1623-2010-04.html
@@ -10,7 +10,7 @@
 <body>
 <cave>
 <non_public>False</non_public><!-- 'False' or 'True'. True if the cave should only be visible to logged-in users. Caves are normally public, so enter 'False' unless you know otherwise. -->
-<caveslug>2010-04</caveslug><!--(Required). Internal I.D. used to refer to this cave in entrance data files. Typically the same as the filebase, e.g. '1623-195'  -->
+<caveslug>1623-2010-04</caveslug><!--(Required). Internal I.D. used to refer to this cave in entrance data files. Typically the same as the filebase, e.g. '1623-195'  -->
 <official_name></official_name><!-- Name of the cave (normally in German)  Use &uuml; for u+Umlaut and &ouml; for o+umlaut eg H&ouml;hle for Hohle and Gl&uuml;ck for Gluck-->
 <area>1623</area><!-- the CUCC-defined areas shown in http://expo.survex.com/areas.htm -->
 <kataster_code></kataster_code><!-- 'length-or-depth/type exploration'
@@ -32,7 +32,7 @@ code used in the Austrian kataster e.g '1/S +' - https://expo/.survex.com/katast
 <unofficial_number>2010-04</unofficial_number><!-- (Either this or kataster_number is required). Initial temporary cave ID used until kataster number is allocated e.g. '2012-DD-01'-->
 
 <entrance>
-  <entranceslug>2010-04</entranceslug><!-- Internal ID to refer to each entrance instance in the entrance files (typically the same as that filename (e.g. 1623-161c). Matches the 'slug' field in the entrance file -->
+  <entranceslug>1623-2010-04</entranceslug><!-- Internal ID to refer to each entrance instance in the entrance files (typically the same as that filename (e.g. 1623-161c). Matches the 'slug' field in the entrance file -->
   <letter></letter><!--Leave blank for single-entrance cave. If there is more than one entrace then the letter needs to be given. Generally matches the entranceslug ID.  -->
 </entrance>
 
diff --git a/entrance_data/2010-04.html b/entrance_data/1623-2010-04.html
similarity index 98%
rename from entrance_data/2010-04.html
rename to entrance_data/1623-2010-04.html
index 902ebbab2..65d5b4bcc 100644
--- a/entrance_data/2010-04.html
+++ b/entrance_data/1623-2010-04.html
@@ -14,7 +14,7 @@
 <body>
 <entrance>
 <non_public>False</non_public>
-<slug>2010-04</slug>
+<slug>1623-2010-04</slug>
 <name></name>
 <entrance_description></entrance_description>
 <explorers></explorers>
