diff --git a/htdocs/core/modules/import/import_csv.modules.php b/htdocs/core/modules/import/import_csv.modules.php
index da927dbdbe1..8f25a38d322 100644
--- a/htdocs/core/modules/import/import_csv.modules.php
+++ b/htdocs/core/modules/import/import_csv.modules.php
@@ -401,7 +401,7 @@ class ImportCsv extends ModeleImports
 						// Make some tests on $newval
 
 						// Is it a required field ?
-						if (preg_match('/\*/',$objimport->array_import_fields[0][$val]) && ($newval==''))
+						if (preg_match('/\*/',$objimport->array_import_fields[0][$val]) && ((string) $newval==''))
 						{
 							$this->errors[$error]['lib']=$langs->trans('ErrorMissingMandatoryValue',$key);
 							$this->errors[$error]['type']='NOTNULL';
diff --git a/htdocs/core/modules/import/import_xlsx.modules.php b/htdocs/core/modules/import/import_xlsx.modules.php
index 47c5fa3feaf..34139820ba8 100644
--- a/htdocs/core/modules/import/import_xlsx.modules.php
+++ b/htdocs/core/modules/import/import_xlsx.modules.php
@@ -419,7 +419,7 @@ class Importxlsx extends ModeleImports
 						// Make some tests on $newval
 
 						// Is it a required field ?
-						if (preg_match('/\*/',$objimport->array_import_fields[0][$val]) && ($newval==''))
+						if (preg_match('/\*/',$objimport->array_import_fields[0][$val]) && ((string) $newval == ''))
 						{
 							$this->errors[$error]['lib']=$langs->trans('ErrorMissingMandatoryValue',$key);
 							$this->errors[$error]['type']='NOTNULL';