diff --git a/htdocs/core/modules/import/import_csv.modules.php b/htdocs/core/modules/import/import_csv.modules.php
index 776d8dfa04f..e0ec89379af 100644
--- a/htdocs/core/modules/import/import_csv.modules.php
+++ b/htdocs/core/modules/import/import_csv.modules.php
@@ -497,7 +497,7 @@ class ImportCsv extends ModeleImports
 								{
 									$field=$reg[1];
 									$table=$reg[2];
-									$filter=substr($reg[3], 1);
+									$filter=!empty($reg[3])?substr($reg[3], 1):'';
 
 									$cachekey = $field.'@'.$table;
 									if(! empty($filter)) $cachekey.= ':'.$filter;
diff --git a/htdocs/core/modules/import/import_xlsx.modules.php b/htdocs/core/modules/import/import_xlsx.modules.php
index d58fd16cf2f..7d850ccfb8b 100644
--- a/htdocs/core/modules/import/import_xlsx.modules.php
+++ b/htdocs/core/modules/import/import_xlsx.modules.php
@@ -523,7 +523,7 @@ class ImportXlsx extends ModeleImports
 								{
 									$field=$reg[1];
 									$table=$reg[2];
-									$filter=substr($reg[3], 1);
+									$filter=!empty($reg[3])?substr($reg[3], 1):'';
 
 									$cachekey = $field.'@'.$table;
 									if(! empty($filter)) $cachekey.= ':'.$filter;