diff --git a/poi-ooxml/src/test/java/org/apache/poi/xssf/usermodel/TestXSSFWorkbook.java b/poi-ooxml/src/test/java/org/apache/poi/xssf/usermodel/TestXSSFWorkbook.java
index e8c7e5ad14..4b3e4d1f8e 100644
--- a/poi-ooxml/src/test/java/org/apache/poi/xssf/usermodel/TestXSSFWorkbook.java
+++ b/poi-ooxml/src/test/java/org/apache/poi/xssf/usermodel/TestXSSFWorkbook.java
@@ -1232,7 +1232,7 @@ public final class TestXSSFWorkbook extends BaseTestXWorkbook {
             XSSFCell cell = row2.createCell(0);
 
             b.linkExternalWorkbook(nameA, a);
-            String formula = String.format("SUM('[%s]Sheet0'!A1:B1)", nameA);
+            String formula = String.format(LocaleUtil.getUserLocale(), "SUM('[%s]Sheet0'!A1:B1)", nameA);
             cell.setCellFormula(formula);
             XSSFFormulaEvaluator evaluator = b.getCreationHelper().createFormulaEvaluator();
             evaluator.evaluateFormulaCell(cell);