diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index c3227489507..fc743889b28 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -185,7 +185,7 @@ function isASecretKey($keyname)
 
 
 /**
- * Return a numeric value into an Excel like column number. So 1 return 'A', 2 returns 'B'..., 27 return 'AA'
+ * Return a numeric value into an Excel like column number. So 0 return 'A', 1 returns 'B'..., 26 return 'AA'
  *
  * @param	int|string		$n		Numeric value
  * @return 	string					Column in Excel format
diff --git a/htdocs/core/modules/import/import_xlsx.modules.php b/htdocs/core/modules/import/import_xlsx.modules.php
index a058fd0174a..c3339a0a138 100644
--- a/htdocs/core/modules/import/import_xlsx.modules.php
+++ b/htdocs/core/modules/import/import_xlsx.modules.php
@@ -1,6 +1,6 @@
 <?php
-/* Copyright (C) 2006-2012	Laurent Destailleur	<eldy@users.sourceforge.net>
- * Copyright (C) 2009-2012	Regis Houssin		<regis.houssin@inodbox.com>
+/* Copyright (C) 2006-2012 Laurent Destailleur	<eldy@users.sourceforge.net>
+ * Copyright (C) 2009-2012 Regis Houssin		<regis.houssin@inodbox.com>
  * Copyright (C) 2012      Christophe Battarel  <christophe.battarel@altairis.fr>
  * Copyright (C) 2012-2016 Juanjo Menent		<jmenent@2byte.es>
  *
@@ -446,7 +446,7 @@ class ImportXlsx extends ModeleImports
 
 						// Is it a required field ?
 						if (preg_match('/\*/', $objimport->array_import_fields[0][$val]) && ((string) $newval == '')) {
-							$this->errors[$error]['lib'] = $langs->trans('ErrorMissingMandatoryValue', num2Alpha($key));
+							$this->errors[$error]['lib'] = $langs->trans('ErrorMissingMandatoryValue', num2Alpha($key - 1));
 							$this->errors[$error]['type'] = 'NOTNULL';
 							$errorforthistable++;
 							$error++;
diff --git a/htdocs/imports/import.php b/htdocs/imports/import.php
index 4209b5e9e96..bf335b9714b 100644
--- a/htdocs/imports/import.php
+++ b/htdocs/imports/import.php
@@ -1743,7 +1743,7 @@ if ($step == 5 && $datatoimport) {
 		}
 		//print $code.'-'.$label;
 		$alias = preg_replace('/(\..*)$/i', '', $label);
-		$listfields[$i] = $langs->trans("Field").' '.$code.'->'.$label;
+		$listfields[$i] = $langs->trans("Column").' '.num2Alpha($code - 1).' -> '.$label;
 	}
 	print count($listfields) ? (join(', ', $listfields)) : $langs->trans("Error");
 	print '</td></tr>';
diff --git a/test/phpunit/FunctionsLibTest.php b/test/phpunit/FunctionsLibTest.php
index 1bf3b6378fb..82205369c86 100644
--- a/test/phpunit/FunctionsLibTest.php
+++ b/test/phpunit/FunctionsLibTest.php
@@ -166,6 +166,26 @@ class FunctionsLibTest extends PHPUnit\Framework\TestCase
 		print __METHOD__."\n";
 	}
 
+	/**
+	 * testNum2Alpha
+	 *
+	 * @return void
+	 */
+	public function testNum2Alpha()
+	{
+		$result = num2Alpha(0);
+		print __METHOD__." result=".$result."\n";
+		$this->assertEquals($result, 'A', 'Check num2Alpha 0');
+
+		$result = num2Alpha(5);
+		print __METHOD__." result=".$result."\n";
+		$this->assertEquals($result, 'F', 'Check num2Alpha 5');
+
+		$result = num2Alpha(26);
+		print __METHOD__." result=".$result."\n";
+		$this->assertEquals($result, 'AA', 'Check num2Alpha 26');
+	}
+
 	/**
 	 * testIsValidEmail
 	 *