diff --git a/phpBB/adm/style/acp_storage.html b/phpBB/adm/style/acp_storage.html
index 2d871a6e44..5107385834 100644
--- a/phpBB/adm/style/acp_storage.html
+++ b/phpBB/adm/style/acp_storage.html
@@ -21,7 +21,11 @@
 			<td>{{ lang('STORAGE_' ~ storage.get_name | upper ~ '_TITLE') }}</td>
 			<td>{{ storage.get_num_files }}</td>
 			<td>{{ storage.get_size | format_bytes }}</td>
-			<td>{{ storage.free_space | format_bytes }}</td>
+			{% if storage.free_space !== false %}
+				<td>{{ storage.free_space | format_bytes }}</td>
+			{% else %}
+				<td>{L_STORAGE_UNKNOWN}</td>
+			{% endif %}
 		</tr>
 	{% endfor %}
 	</tbody>
diff --git a/phpBB/language/en/acp/storage.php b/phpBB/language/en/acp/storage.php
index 1f43c6963a..5e171ac6f0 100644
--- a/phpBB/language/en/acp/storage.php
+++ b/phpBB/language/en/acp/storage.php
@@ -47,6 +47,7 @@ $lang = array_merge($lang, array(
 	'STORAGE_NUM_FILES'				=> 'Number of files',
 	'STORAGE_SIZE'					=> 'Size',
 	'STORAGE_FREE'					=> 'Available space',
+	'STORAGE_UNKNOWN'				=> 'Unknown',
 
 	// Storage names
 	'STORAGE_ATTACHMENT_TITLE'		=> 'Attachments storage',